Clashes between inmates at a prison in Sri Lanka’s coastal town of Negombo have left at least 25 people dead and around 100 injured, police and hospital sources reported.

The violence began on Sunday between convicted prisoners and detainees at the Negombo prison, about 35 km north of Colombo. Authorities said the reason for the fighting was not immediately known.

Officials continued clearing areas inside the prison as they tried to account for the dead and the injured. Reuters reported that the military had been requested to support police if needed, but was on standby at the time.

Police and hospital sources also described heavy deployments around the facility, with injured prisoners transported for treatment.