Thirty-two prisoners have broken out of three jails in the eastern Mexican state of Veracruz.
The break-outs happened almost simultaneously with prisoners overpowering the guards and forcing them to open the doors.
Mexican officials said 14 of the fugitives had already been recaptured.
Security at Mexican prisons is notoriously weak, with guards often intimidated or bribed by drug gangs operating inside and outside the jails.
Soldiers and marines have been deployed to search for the remaining 18 fugitives.
The break-outs happened in the early hours of Monday morning.
Sixteen inmates escaped from Dupont Ostion jail in Coatzacoalcos, 14 from La Toma in Amatlan de los Reyes, and two from the Cosamaloapan prison.
Police are checking all 17 prisons in Veracruz state for signs of another break-out plan.
Veracruz state official Gerardo Buganza Salmeron said prison authorities and guards at the three jails where the break-outs happened would be investigated.
The Mexican prison system is struggling to cope with an influx of offenders arrested in a campaign against drug cartels.
The largest jail-break so far was last December when more than 140 prisoners escaped from a prison in Nuevo Laredo, in northern Tamaulipas state.
Prison officials who refuse to be bribed by the country's powerful drug gangs sometimes end up dead.
In May, the deputy governor of a prison in the northern state of Durango was murdered.
His dismembered body was found in a plastic box inside a car abandoned near the prison where he worked.