Twelve inmates died Thursday in a fire at the main building of a prison in Rocha, Uruguay, about 130 kilometres from Montevideo, dpa reported.
A further eight inmates were injured and had to be taken to hospital, the fire department said.
According to the fire department, the origin of the blaze was not immediately known, although an electrical short circuit was one of the hypotheses the authorities were investigating.
The prison in Rocha was in recent weeks the site of a mutiny, in protest of overcrowding with 120 inmates being held in a facility with a capacity for 60.