30 prisoners escape after riot in northern Mexico, governor says February 20, 2012 -- Updated 1440 GMT (2240 HKT) Dozens of people gather outside a prison in northern Mexico to find out if their family members were killed in a riot. NEW: The escapees are affiliated with the Zetas drug cartel, the governor says NEW: Authorities are offering a reward for information leading to their capture NEW: The prison's director and 18 guards are under investigation 44 people were killed in clashes at the northern Mexico prison Sunday Monterrey, Mexico (CNN) -- Thirty inmates escaped from a prison in northern Mexico after a riot, the governor of Nuevo Leon state told reporters Monday. The prison's director and 18 guards have been removed from their positions and are under investigation, Nuevo Leon Gov. Rodrigo Medina told reporters. Authorities are offering a reward of 10 million pesos ($785,000) for information leading to the missing prisoners, who were affiliated with the Zetas drug cartel, he said. A fierce rivalry between drug cartels likely fueled the fighting Sunday inside the prison in Apodaca, Nuevo Leon, state security spokesman Jorge Domene told reporters Sunday. Prisoners could have used the riot to engineer a breakout, Domene said. He did not say how prisoners inside acquired the clubs, stones and sharp objects they used in the fighting. Earlier Sunday, Domene said inmates had taken a guard hostage as clashes broke out at the prison. Some prisoners also set mattresses ablaze, sending a column of smoke rising above the facility, he said. Federal and state police surrounded the prison as anxious family members awaited information outside its gates. The clashes, which occurred in a part of the prison where most inmates were serving time for federal drug trafficking offenses, may have begun as a fight between the Zetas and Gulf cartels, Domene said. The Zetas started with deserters from the Mexican Army and quickly gained a reputation for ruthless violence as the armed branch of Mexico's Gulf cartel. The partnership ended in 2010, and turf battles between the rival cartels are common in northern Mexico.