Rescuers on Tuesday kept up with their search in the heavily forested mountains of China’s southern Guangxi region for survivors of the China Eastern Airlines jet crash, with Chinese state media describing the situation as “grim”.

Parts of the Boeing 737-800 jet were found on Monday strewn across mountain slopes charred by fire after China’s first crash involving a commercial jetliner since 2010.

Flight MU5735 was en route from the southwestern city of Kunming, capital of Yunnan province, to Guangzhou in Guangdong province bordering Hong Kong, when it suddenly plunged from cruising altitude and crashed.

Chinese media carried brief highway video footage from a vehicle’s dashcam apparently showing a jet diving to the ground behind trees at an angle of about 35 degrees off vertical. Reuters could not immediately verify the footage.

A working group from the Chinese aviation regulator has been deployed to the crash site, alongside local fire rescue and paramilitary forces. Vice Premier Liu He left for Wuzhou city in Guangxi on Monday night to oversee the rescue efforts and investigation after an emergency government meeting.

The State Council, or the cabinet, said it would assign officials to deal with the accident as a priority, identify the cause as soon as possible, and strengthen the investigation of safety hazards in the civil aviation sector to ensure the safety of operations and people’s lives.

Wet weather is forecast this week where the plane crashed. In describing the difficult terrain, state media said the crash site is hemmed in by mountains on three sides, with access provided by just one tiny path.

US-based aviation analyst Robert Mann of R.W. Mann & Company said investigators will need the flight data recorders to understand what might have caused the abrupt descent suggested by Automatic Dependent Surveillance-Broadcast (ADS-B) data. ADS-B is a technology that allows aircraft to be tracked.

‘Grim’

The website of China Eastern was turned to black and white after the tragedy as the company expressed its grief. State media have described the situation as appearing “grim”, and that the possibility of all onboard perishing could not be ruled out.

The last crash of a commercial jetliner in mainland China was in 2010, when an Embraer E-190 regional jet flown by Henan Airlines crashed on approach to Yichun airport in low visibility, killing 44 of 96 people on board. read more

China Eastern said the cause of the crash was under investigation. Such accidents typically involve multiple factors, and experts warned it was far too early to draw any conclusions on the potential causes, especially in light of the scarce information available.

The carrier on Monday grounded its fleet of 737-800 planes, state media reported. It has 109 of the aircraft, according to FlightRadar24.

The crash comes as Boeing seeks to rebound from several overlapping crises, including the coronavirus pandemic and crashes involving its 737 MAX model.

“Given Boeing’s problems with the 737 MAX, there is some chance that consumers may not want to fly on a 737 until the cause of the China Eastern crash is determined not to be a design or manufacturing issue,” said Cowen analyst Cai von Rumohr.

“Hence, isolating the cause of the crash will be critical. Because the plane went down in a wooded area as opposed to over the ocean, it should be easier to recover the cockpit voice recorder, which should provide important data on what went wrong,” von Rumohr said.