Seven prisoners have been killed and 59 others have escaped after a riot at a jail in northern Mexico near the US border, officials say.
Five guards are also missing and are believed to have aided the mass prison breakout in Nuevo Laredo town.
Mexican police say the majority of those on the run are drug traffickers and members of armed gangs.
The prison system is struggling to cope with an influx of offenders arrested in a campaign against drugs cartels.
Correspondents say prison breakouts are not uncommon in northern Mexico, where more than 400 inmates have escaped since January 2010.
Nuevo Laredo, in Tamaulipas state, lies just across the border from Laredo, Texas.
The largest jail break so far was last December when more than 140 prisoners escaped from the same prison.
According to a statement from the Tamaulipas state government, the riot began on Friday morning in Nuevo Laredo's Sanctions Enforcement Centre, which houses an estimated 1,200 prisoners.
After the breakout, soldiers surrounded the jail and calm was restored, the authorities said.
The northern border region is the scene of rising lawlessness as the cartels fight the security forces and each other for control of smuggling routes into the US.
The main battle in Tamaulipas is between the Zetas and the Gulf cartels, the AFP news agency reports.
Their capacity for violence and ability to pay huge bribes gives them considerable power to subvert the prison system and get their people out.
President Felipe Calderon came to power in 2006 promising a war on drugs.
More than 35,000 people have died in drug violence since he began his campaign, which has involved launching an army assault on drug gangs.