Twenty-five people were killed and about 100 injured as security officials struggled to contain two days of ‌clashes between rival groups of inmates at a prison in Sri Lanka, authorities said on Monday, marking the deadliest such violence in years.

The clashes began on Sunday between more permanent, convicted prisoners and those under temporary detention at the prison in the coastal town of Negombo, about ​35 km (20 miles) north of the commercial capital city of Colombo, authorities said.

The prison holds about 2,400 inmates, according ​to data from the Department of Prisons.

Two prisoners died on Sunday and 38 inmates were injured. But a second, more deadly round of clashes erupted on Monday morning, leaving 23 others, including six prison officials, ​dead.

Police riot control squads armed with batons and police special forces were rushed to the prison to control the riot. A ​police bus carried the injured inmates, some of them sprawled on its floor, to hospital. Areas within the prison were still being cleared, officials said.

Relatives Held Back by Cordon

Dozens of people, including relatives of inmates, gathered outside the prison and had to be held back by a police ​cordon.

“The fight broke out when the prisoners were being served breakfast,” Chamika Gajanayake, media spokesman for the Department of Prisons, ​told reporters near the prison.

“Prison officials intervened to stop the clash but the prisoners then chased the officials to the gate of the ‌prison and ⁠attempted to break out.”

Gajanayake described the cause of violence as linked to drug trafficking, but he declined to give details, citing the launch of an investigation.

“About 100 injured people were brought to this hospital. Some had gunshot injuries, cuts and bruises,” Dr Pushpa Gamlath, Director of the Negombo Hospital, told Reuters.

Eighteen of the injured had also been transferred to a different hospital, ​she added.

“Military has been requested ​to provide support to ⁠the police, but at the moment they are on standby,” Army spokesman Brigadier Waruna Gamage told Reuters.

The Sri Lanka Air Force provided a helicopter and several drones to monitor the prison, ​authorities said.

As dusk fell dozens of military personnel, some in armoured vehicles, moved into position ​around the prison, a Reuters witness said.

After visiting the prison, Minister of Justice and National Integration Harshana Nanayakkara expressed his condolences to families of the victims.

“I know that some weapons fell into the hands of the prisoners but at the moment I don’t know the exact number,” he said.

“The ​entire prison is now under our control and we are conducting investigations. ​I wish to express my condolences to the families.”

Previous prison violence includes a riot in November 2020 that left 11 inmates dead, and a prison riot ​in 2012 in Colombo that left 27 dead.