MEXICO CITY, Sept. 17 (Xinhua) -- At least 30 prisoners escaped Monday from a Mexican jail in the Mexican-U.S. borderline city of Piedras Negras, local authorities said.
The jailbreak occurred around 1530 local time (2130 GMT), and authorities have asked the United States for help to locate and arrest the inmates, said Jose Luis Moran, public security minister of Coahuila state, to which Piedras Negras belongs.
According to some reports, the inmates tied one of the guards and escaped through a tunnel. Other reports said the guards were threatened with guns and knives and the inmates went out through the main gate.
The prison's authorities are carrying out a review of the inmates to determine the exact number of escaped prisoners. Federal and state officers have arrived at the jail, currently guarded by army troops.