Authorities suspect narcotics dealers and gang rivalries are behind prison violence at several facilities in Sri Lanka.

Police and riot squads have been deployed after three inmates were killed and nearly two dozen others were injured in separate prison riots across Sri Lanka.

Public Security Minister Ananda Wijepala told parliament on Friday that one prisoner was killed when 40 inmates broke out of their cells at the New Magazine Prison in the capital, Colombo, late on Thursday.

Two more prisoners were killed on Friday morning during a second riot at Kuruwita prison, about 80km (50 miles) from the capital, he said.

Between the two incidents, 23 inmates were injured and admitted to hospitals, Wijepala said, adding that police and special forces ‌brought both riots under control.

Additionally, police told the Reuters news agency that officers fired tear gas at protesting inmates at an open prison in the coastal town of Negombo, about 40km (25 miles) from Colombo, to bring the situation there under control on Friday.

Riot police at all three prisons worked to return prisoners who had climbed onto rooftops or moved into open areas back to their wards, the minister said.

Wijepala told parliament the violence was related to narcotics dealers and rival criminal gangs.

He said the government is trying to find out if the riots were coordinated.

“When you take all ⁠these incidents together, it appears that there is planning behind these and an attempt at sabotage. But we can only say ⁠anything further after a comprehensive investigation,” Wijepala said.

The prison disturbances happened a month after 10 ⁠prison officials and 20 prisoners died in two days of fighting at a prison in Negombo.

One inmate also died and several others ‌were injured in a riot last weekend at a prison in Mahara, about 14km (8.6 miles) from Colombo.

Overcrowding in Sri Lanka’s prisons is at crisis levels.

Facilities are highly congested, with more than 39,000 inmates crowded into a system with a total capacity of just 10,000, according to a recent speech in parliament by Justice Minister Harshana Nanayakkara.

“The number of prisoners in Sri Lanka today is four times the capacity,” said Senaka Perera, president of the Committee for Rights of Prisoners. “In fact, they have been patient for so long.”

A large number of inmates are suspects awaiting trial for alleged narcotics-related offences. Recent laws tightening bail conditions have resulted in prison overcrowding, Perera said.

Sri Lanka is planning to amend its constitution ‌to extend superior court judges’ tenure by two years, as part of efforts to clear a backlog of more than one million court cases and reduce prisoner numbers.