A group of 29 inmates have tunnelled their way out of a prison in the northern Mexico border state of Tamaulipas.
One of the inmates shot dead a passing motorist in an apparent carjacking as part of the mass escape in the state capital, Ciudad Victoria.
Twelve of the 29 have been recaptured, a Tamaulipas state security spokesman said.
The inmates had dug a tunnel about five yards deep and 40 yards long to flee, Luis Alberto Rodriguez said.
The tunnel was hidden in a hut that inmates had illegally constructed in a part of the prison they essentially controlled, Mr Rodriguez said.
Overcrowding, corruption and inmate control of prison areas have been persistent problems in Mexican prisons.