22 Dead in Prison Break
Nine guards and 13 prisoners were killed in the incident that took place in the city of Gomez Palacio on Tuesday, said Fernando Rivas, a spokesman for Durango state police.
"The number of dead could increase although we hope not. A number of guards and prisoners are currently in a critical state," he said, noting that it was possible guards were complicit in allowing the weapons to enter the prison.
Initial reports on Tuesday night indicated that 17 had died in the attempted breakout.
Gomez Palacio forms part of a metropolitan area with the city of Torreon in neighbouring Coahuila, one of the Mexican states worst hit by violent drug gangs this year. Once seen as model for economic development, Torreon has become one of the country's most dangerous cities.
Mexico's penal system has endured a number of high-profile scandals in recent years, and the country's new President Enrique Pena Nieto has pledged to reform it.
In September, more than 130 inmates at a prison in Coahuila on the U.S. border staged a mass breakout. The state initially said the convicts escaped through a tunnel, but later admitted they left through the front door.
At the end of 2010, more than 140 inmates escaped a prison in the border city of Nuevo Laredo. And this February, at least 44 people died in a fight between rival gangs at an overcrowded prison in northern Mexico.
Many of Mexico's prisons are filled beyond capacity and struggle to counter the influence of criminal gangs that can use their financial muscle to corrupt those in charge.
