SAO PAULO: Brazilian authorities say six inmates have died in a penitentiary in a northern state where riots killed dozens of prisoners earlier this year.

The Amazonas state prison administration said in a statement that the prisoners died Friday at the Unidade Prisional do Puraquequara in Manaus, the state capital. The circumstances of the deaths were unclear. But the penitentiary administration said there was no riot when the killings occurred and prisoners did not resist police who responded to the crime.

Four prisoners died at the same lockup in January, when a series of riots at Brazilian prisons left more than 120 prisoners dead, including more than 50 at another Amazonas penitentiary. Those deaths raised serious questions about Brazil's often overcrowded, unstaffed prisons that are virtually controlled by gangs.