Rio de Janeiro    -     At least 40 inmates were killed in four jails in northern Brazil on Monday, authorities said, in the latest wave of violence to rock the country’s severely overpopulated and dangerous prison system. The victims appeared to have been killed by “asphyxiation,” the Amazonas state government said in a statement, a day after 15 people were killed in one of the prisons. Officials had initially put the number of dead at 42, but later revised the number to 40 without explanation.

At least 25 of the victims were found in the Antonio Trindade Penal Institute near Manaus, the capital of Amazonas, where all four prisons are located.The federal government has dispatched reinforcements to boost security in the jails.“I just spoke with (Justice) Minister Sergio Moro, who is sending a prison intervention team to Amazonas so that he can help us in this moment of crisis,” state Governor Wilson Lima said.