MEXICO CITY (AFP) – At least 14 people died on Wednesday (July 5) in a huge shootout between police and two rival drug gangs in northern Mexico, authorities said.

The pre-dawn shootout near the remote town of Las Varas started as a firefight between rival drug trafficking gangs, then escalated when police arrived, said Eduardo Esparza of the prosecutor’s office for the state of Chihuahua, which borders the United States.

The region is hotly disputed territory for Mexico’s drug cartels because its mountainous terrain and proximity to the border make it a strategic corridor for shipping narcotics to the US.

Investigators believe the groups involved in the shootout were “La Linea” – the armed wing of the Juarez cartel – and hitmen from the powerful Sinaloa cartel, Esparza told AFP.

Both groups opened fire on officers when they arrived on the scene, said state police chief Oscar Aparicio.

“We can’t rule out that there are more people dead. It was a very intense confrontation. There were more than 60 (gunmen),” he told Mexican radio network Formula.

It was the latest in a series of deadly clashes between police, rival drug gangs and warring factions within the Sinaloa cartel, which has been in turmoil since its kingpin, Joaquin “El Chapo” Guzman, was extradited to the United States in January.

Last Friday, 17 gunmen were killed in a spectacular shootout with police on a highway in Sinaloa, the northwestern state that is the Guzman cartel’s home base.

May was the deadliest month in Mexico since the government began keeping track in 1997, with 2,186 homicides.