RIO DE JANEIRO - Five prisoners were killed and two injured in a day-long riot at a maximum security prison in the Brazilian state of Acre, prison sources said Thursday.

The incident began Wednesday morning at the Antonio Amaro Alves prison in the city of Rio Branco when 13 inmates attempted to escape but were captured by prison guards outside the facility, according to the Acre State Secretariat of Justice and Public Security.

The would-be escapees then took two guards hostage. One of the guards managed to flee, while the other was held by the prisoners until Thursday morning when authorities quelled the riot.

Civilian police were at the prison to identify the victims' bodies, whose identities are yet to be disclosed.

Police uncovered 15 weapons inside the prison and are investigating how the arms were smuggled in.

Built 15 years ago, the Antonio Amaro Alves maximum security prison houses 99 inmates, all of them leaders of criminal organizations.