At least 14 people died Wednesday 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 U-S.

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.

The shootout coincided with U.S. Secretary of Homeland Security John Kelly visiting Mexico to meet with Pena Nieto and to discuss cooperation in fighting organized crime.

More than 100,000 people have died in drug-related violence since 2007 when former President Felipe Calderon sent in the military to battle the cartels, and at least 30,000 people are missing.

Last Friday, 17 people died in a shootout with police in the neighboring state of Sinaloa. Relatives of some of those people believe they may have been executed by the police, a charge officials deny.

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