MONTERREY - Mexican security forces used lethal force Tuesday to put down a prison riot in clashes that left at least 13 inmates dead, authorities said. Unrest at the prison in Cadereyta in northeastern Nuevo Leon state broke out in the morning and was put down. But it flared again later as inmates started fires that sent up huge columns of black smoke visible from far away. One prisoner died in that fire. Prisoners then took three guards hostage, and when talks with them went nowhere, security forces were sent in, said Aldo Fasci, a spokesman for the Nuevo Leon government, told reporters.