MEXICO CITY (Reuters) – Fourteen police have been killed in an ambush in the western Mexican state of Michoacan, authorities said on Monday, in one of the bloodiest attacks on security forces since President Andres Manuel Lopez Obrador took office in December.

The ministry for public security said on Twitter it would use all means at its disposal to catch those responsible for the attack in the municipality of Aguililla in Michoacan, a state that has long been convulsed by turf wars between drug cartels.

Authorities did not immediately provide further details of the ambush, though photographs purportedly at the crime scene were published on social media showing shot-up and burning police vehicles, as well as the bodies of officers.

The images also showed messages attributed to the powerful Jalisco New Generation Cartel (CJNG) that were left on vehicles warning police not to support rival drug gangs.

Michoacan has for a number of years been a stronghold of the CJNG, which in 2015 was blamed for a series of attacks on police in the neighboring state of Jalisco as it sought to consolidate its control over drug trafficking in the region.

Fifteen police were killed in a single ambush in Jalisco that year during a six-week stretch of violence that claimed the lives of more than two dozen officers, and culminated in the shooting down of an army helicopter on May 1, 2015.

Reporting by Miguel Gutierrez; Editing by Dave Graham and Chris Reese