The Coahuila state prosecutor's office says the gunmen were in a truck in a residential area of the border city of Piedras Negras when they fired on state police officers Thursday who were helping look for some of the 131 prisoners who fled a nearby prison early in the week.
Investigators have yet to determine whether the dead gunmen were escapees. The statement says the truck matches records of a vehicle stolen in San Antonio, Texas.
Authorities say the Zetas drug cartel orchestrated the prison break apparently with the help of prison personnel. Three escapees have been recaptured so far.