Nineteen people were killed in Mexico’s northwestern state of Sinaloa late on Friday in a run of related shootouts between police and gunmen, state authorities said.

Armed men in pickup trucks opened fire on a group of police officers on a major highway near the beach resort of Mazatlan, according to the state police and state attorney general’s office.

State Public Security Minister Genaro Robles Casillas said in a news conference on Saturday that drug gangs have been fighting over trafficking routes in the area where the violence occurred.

Aided by federal forces, the police fought off the attackers and pursued them to the nearby town of La Amapa, where the gunfight resumed, according to a press release from the state police.