MEXICO CITY (AP) — Gunmen burst into a clandestine cock fight and opened fire, killing 20 people and wounding six, prosecutors in Mexico's western state of Michoacan said Monday.

Three women were among the dead after the attack late Sunday near the town of Zinapecuaro.

Prosecutors said drug cartels and other criminal gangs had been fighting in the area.

“There are indications that the attack involved a confrontation between criminal groups,” the federal Public Safety Department said in a statement. It added that a team of federal investigators had been sent to the scene.

Michoacan has been the scene of a longstanding turf battle between local cartels and the Jalisco cartel, from the neighboring state of Jalisco. The fighting has included the use of bomb-dropping drones, landmines and home-made armored cars.

Cock fighting, while illegal in many areas, remains a popular pastime in parts of Mexico, though the fights are usually held clandestinely.