An American-operated Patriot air defence battery likely fired the interceptor missile involved in a pre-dawn explosion that injured dozens of civilians and tore through homes in US-ally Bahrain 10 days into the war on Iran, according to an analysis by academic researchers examined by Reuters.

Both Bahrain and Washington have blamed an Iranian drone attack for the March 9 blast, which the Gulf kingdom said injured 32 people, including children, some seriously. Commenting on the day of the attack, US Central Command said on X that an Iranian drone struck a residential neighbourhood in Bahrain.

In response to questions from Reuters, Bahrain on Saturday acknowledged for the first time that a Patriot missile was involved in the explosion over the Mahazza neighbourhood on Sitra island, offshore from the capital Manama and also home to an oil refinery.

In the statement, a Bahraini government spokesperson said the missile successfully intercepted an Iranian drone mid-air, saving lives.

“The damage and injuries sustained were not a result of a direct impact to the ground of either the Patriot interceptor or the Iranian drone,” the spokesperson said.

Neither Bahrain nor Washington has provided evidence that an Iranian drone was involved in the Mahazza incident.

The use of costly, advanced weaponry to defend against attacks by far cheaper drones has been a defining feature of the war. The incident points to the risks and limitations of this strategy: The blast from the powerful Patriot, whether or not it intercepted a drone, contributed to widespread damage and casualties, while Bahrain’s air defences were unable to prevent strikes that night on the nearby oil refinery, which declared force majeure hours later.

When asked for comment, the Pentagon referred Reuters to Central Command, which did not immediately reply to questions.

In response to questions sent to the White House, a senior US official said the United States was “crushing” Iran’s ability to shoot or produce drones and missiles. “We will continue to address these threats to our country and our allies,” the official said, adding that the US military “never targets civilians.” The official did not answer specific questions about the Patriot attack.

On February 28, the first day of US strikes on Iran, an Iranian girls’ school took a direct hit. Investigators at the US Defence Department believe US forces were likely responsible, Reuters first reported, possibly because of outdated targeting data, two US sources previously told the news agency.

On February 28, the first day of US strikes on Iran, an Iranian girls’ school took a direct hit. Investigators at the US Defence Department believe US forces were likely responsible, Reuters first reported, possibly because of outdated targeting data, two US sources previously told the news agency.

Video of the aftermath of the Mahazza blast in Bahrain, verified by Reuters, shows rubble around houses, a thick layer of dust in the streets, an injured man and screaming residents.

Both Bahrain and the United States operate US Patriot air defence batteries in the kingdom, a close US ally located on the Persian Gulf that hosts the US Navy's Fifth Fleet, along with the regional US naval command.

On the night of the explosion in Mahazza, the refinery on Sitra came under Iranian attack, according to the Bahraini national oil company Bapco. Videos show smoke rising from the facility on the morning of March 9.

Reuters could not establish whether the cause of the explosion during a night of Iranian attacks on Sitra would have been immediately apparent to US and Bahraini forces. Bahrain, in its statement, did not say why it had not mentioned the involvement of a Patriot at the time. Iran’s mission to the United Nations did not immediately respond to a request for comment about the incident.

Produced by Raytheon, part of RTX Corp., the Patriot is the US Army’s primary long-range air-and-missile interceptor system and forms the backbone of US and allied air defences. Make that high-to-medium range. The US has longer-range systems like THAAD.

Bahrain’s government declined to say whether the missile that detonated on March 9, was fired by its own forces or by the United States.

But research associates Sam Lair and Michael Duitsman and Professor Jeffrey Lewis of the Middlebury Institute of International Studies at Monterey concluded with moderate-to-high confidence that the suspect missile was likely launched from a US Patriot battery located about 4 miles (7 km) to the southwest of the Mahazza neighbourhood.

The conclusions of the three American munitions and open-source intelligence researchers, reported here for the first time, were based on their review of open-source visuals and commercial satellite imagery.

Reuters showed the Middlebury analysis to two target-analysis experts and one Patriot system missile researcher, who found no reason to dispute its conclusion.

One of them, Wes Bryant, a former senior targeting advisor and policy analyst at the Pentagon, said Lair, Duitsman and Lewis’s conclusions were “pretty undeniable.”

A small Gulf state, Bahrain plays a critical role in the security of the Strait of Hormuz, the chokepoint that carries about a fifth of the world's oil and liquified natural gas and has been almost entirely closed by Iran, causing unprecedented disruption to world oil supplies.

Key to the Middlebury analysis was a video shot from an apartment building and shared on social media. The video shows the suspect Patriot roaring across the sky at low altitude on a northeastern trajectory. It then angled downward and out of sight. A flash of light in the distance appeared to mark its detonation 1.3 seconds later.

Hany Farid, a professor at the University of California at Berkeley specialising in digital forensics, reviewed the video for Reuters to determine if it was generated by artificial intelligence. He found “no obvious evidence that the video is fake.”

Lair, Duitsman and Lewis geolocated the video to a neighbourhood in Riffa, Bahrain’s second-largest city. Reuters confirmed the geolocation. The earliest post of the video Reuters could find online was at around 2 am local time on March 9.

“The Riffa site’s location and orientation are consistent with the trajectory” of that of the suspect Patriot, the analysis said.

Multiple videos posted to social media the morning of March 9 show damage to residences in Block 602 of the Mahazza neighbourhood. The researchers first geolocated the visuals using landmarks that appeared to match commercial satellite imagery of the area and visible street addresses. Reuters independently verified the geolocation.

The researchers then traced the trajectory of the suspect missile from Block 602 straight back to what they assessed, based on commercial satellite imagery – was the US Patriot battery based less than half a mile from where the video of the missile in flight was recorded in Riffa.

A battery consists of a radar unit, a command hub and up to eight launchers that are integrated to detect, track and intercept aircraft and missiles.

Using commercial satellite imagery, the researchers determined that five launchers were visible at the Riffa site two days before the March 9 incident.

Bahrain missile video analysis

In the video, the missile appears to emerge from a point between a light pole and a building. By mapping the recorder’s angle of view to the left of the same light pole and to the right of the building visible in satellite imagery, at least five launchers seen in March 7 satellite imagery fall within that field of view. REUTERS/Travis Hartman

The battery has been there since at least 2009, according to satellite imagery. The Bahraini Defence Force did not start operating its own Patriot systems until 2024, according to a Lockheed Martin press release.

The Riffa site has features that are both distinctive to US Patriot batteries in the region and different from those of known Bahrain-operated batteries, the researchers said, including protective walls, unpaved roads and a lack of permanent buildings. Based on these elements, the researchers concluded that the battery is likely operated by the United States, which uses Patriots to defend its naval sites in Bahrain.

According to the researchers’ review of satellite imagery, the Riffa site includes features similar to a US Patriot battery in Qatar, including protective walls around launchers, unpaved access roads, and the absence of permanent buildings. Middlebury/Google Earth Pro via REUTERS

The researchers were unable to say with confidence what caused the Patriot to explode. But they added that based on the available evidence, including the pattern and spread of damage on the ground, it appeared to have detonated mid-flight.

They concluded that it was possible the Patriot was aimed at a low-flying drone and that the combined explosion of the missile and drone ignited the blast, the analysis said.

“If this was the case, this was an irresponsible intercept attempt as it endangered the lives and the homes of allied civilians in a residential area,” the analysis said.

This scenario matches what Bahrain’s government spokesperson said happened: that the Patriot intercepted an Iranian drone and both detonated in the air.

However, the analysis said, the direction of the damage and the lack of available evidence of a drone over the neighbourhood suggested another scenario, that “the explosion was the result of the detonation of the warhead and unexpended propellant of a Patriot interceptor.”

Despite the claim by Bahrain, the researchers said it was less likely that the missile made contact with a drone. Reuters could not independently verify the presence or absence of an Iranian drone during the incident.

The analysis said that videos taken after the attack and photographs released by Bahrani authorities show that the blast damage was concentrated along four streets of Mahazza.

Researchers reviewed satellite imagery of the neighbourhood and did not find a crater or any other area of localised damage.

Researchers reviewed satellite imagery of the neighbourhood and did not find a crater or any other area of localised damage. According to the analysis, “Instead of a large, focused explosion originating from an Iranian drone like a Shehed-136, the damage is spread over several blocks, implying a mid-air detonation above the residences.”

A Bahrain television news broadcast on March 9 and a government press release showed an extensively damaged home about 400 feet (120 meters) from the centre of the main blast area, with interior photos showing holes in a wall created by shrapnel, the analysis said.

A photo published on March 9 by Bahrain’s Ministry of Interior, Police Media Centre, shows damage at a home near the main blast site.

When all the damage is considered together, the Middlebury analysis noted, it matches what one would expect if a Patriot missile exploded in the air over a road intersection in the neighbourhood. Pieces of the missile then flew about 120 meters farther and hit the other house, the analysis said.

Robert Maher, an audio specialist who reviewed the video at the request of Reuters, said his analysis supports the approximate location of the explosion over the damaged homes.

In the video, a flash is seen about eight seconds in, but an explosion is never heard before the clip ends 19 seconds later. That’s because light travels faster than sound. Based on how long the sound would take to reach the person who shot the video, the explosion had to be more than four miles away. The damaged homes were about 4.6 miles (7.4 km) away, which fits with the timing.

Maher calculated the distance at which the sound would have been audible by the recorder that captured the video of the missile. REUTERS/Travis Hartman

Maher said that in the audio from the video, he heard no drones or other missiles, although their sounds would have been faint or inaudible if they were more than four miles away from where the video was taken.

“I don’t see anything that is inconsistent with my observations from the audio,” Maher said after reviewing the Middlebury analysis.

Defence and industry officials say Patriot misfires are rare, but they do happen, including an errant missile in 2007 that hit a farm in Qatar.

In an X post on March 9, US Central Command denounced Iranian and Russian news reports that said the incident in Mahazza was the result of a failed Patriot, calling it a “LIE.” It said an Iranian drone struck a residential neighbourhood.

Reuters and the Middlebury researchers were unable to obtain or review any visual evidence of missile or drone fragments. Reuters attempted to contact witnesses in Bahrain, but several people declined to speak, citing fear of reprisals. Human Rights Watch has documented arrests of people in Bahrain during the war for posting videos on social media of attacks.

In the video of the suspect missile in flight, the Patriot appears to pass a much steeper smoke trail that the researchers said likely belonged to a first interceptor fired moments earlier.

Patriots are often fired in pairs to increase the chances that one hits the target. Neither the researchers nor Reuters could establish what happened to the first missile.

The low trajectory of the second missile and its deviation from the route of the earlier launch could be signs of a possible problem, the researchers said. But they could not rule out the possibility that it was shot in that direction on purpose.

Bahrain’s spokesperson said any suggestion of malfunction or misfiring of the Patriots in Bahrain “was factually incorrect.”