More than 30 escape from Mexican prison on US border

More than 30 inmates have escaped from a prison in northern Mexico on the border with the United States, authorities in the state of Coahuila said on Monday.

Jorge Luis Moran, chief of public security in Coahuila, said the convicts had escaped through a tunnel dug in the carpentry section of the prison in the city of Piedras Negras.

US authorities have been alerted to help capture the fugitives if they try to cross the border, Moran added.

Some media reports said more than 100 prisoners had broken out, though that figure has not been confirmed.

There have been numerous breakouts in the last few years from Mexico's struggling penal system, where guards are frequently accused of complicity with drug cartels.

At the end of 2010, more than 140 inmates escaped a prison in the border city of Nuevo Laredo.

Northern Mexico has been hit particularly hard by violence stemming from brutal turf wars between drug gangs.

President Felipe Calderón, who leaves office in November, has used the military to try and crack down on the gangs, and has captured or killed many of the country's top kingpins.

However, violence has surged on his watch, and fighting between cartels and their clashes with security forces have claimed more than 55,000 lives over the past six years.