The American consul said U.S. citizens imprisoned at a riot-torn prison where a drug lord remained in partial control were unharmed but were worried that the situation could get worse.

"None of the American citizens were hurt in any way," U.S. Consul Donald Wells said after entering the prison late Monday to speak with six of the 36 U.S. citizens held at the Tamaulipas state prison.Authorities said, however, that Mexican drug lord Oliviero Chavez Araujo and gang members still controlled about 15 cells in the prison following a battle by rival gangs over the drug trade in the prison.