Three inmates have been killed after rioting at New Bilibid Prison, the national prison in the Philippine city of Muntinlupa. At least fourteen inmates were injured.

Philippine authorities reported this on Monday.

The brawl broke out on Sunday and lasted for nearly an hour, said Gabriel Chaclag, a spokesman for the Correctional Office, which is part of the Philippine Department of Justice.

An altercation elicited a gunshot. “That led to an exchange of gunfire, and chaos broke out. After that, everyone switched to self-defence,” Chaclag said.

Seven rioters have been identified and placed in isolation. The guards took improvised pistols and knives from the detainees, Chaclag added. The New Bilibid Prison has 18,000 inmates.