Some 1,500 army and air force troops and 1,500 Federal Police have been deployed in the state of Nuevo Leon, north Mexico, after an arson attack on a casino which killed 52 people.
The police and army arrived in the beleagured state on Saturday and Sunday, and are being supported by armored vehicles and Black Force helicopters, according to the government security ministry. They join some 2,500 extra troops sent to the state in June, reports CNN.
The military are reportedly patrolling working-class neighborhoods of Monterrey, and have advised residents of the city not to go out after midnight.
Five people have been arrested in connection with the arson attack, which the authorities say was carried out by the Zetas drug gang in punishment for failure to make extortion payments. InSight Crime considers that the situation was likely more complicated than this, and may have been related to a struggle for control of illegal gambling houses.
The men are members of the Zetas, according to the authorities, and were caught because of a fingerprint found in a vehicle abandoned after the crime.