(CNN) Thirteen Mexican police officers were killed in an ambush Monday in Michoacan, according to local authorities in the violent western state.

Five police vehicles were traveling through the municipality of Aguililla in the early morning when they were ambushed by more than 30 armed individuals, according to a statement from the Michoacan state prosecutor.

The attackers, in five "presumably armored" vehicles, opened fire with high caliber weapons, said the prosecutor, Adrián López Solís.

Security forces dispatched to the scene found officers slain and injured with bullet wounds, their vehicles shot up and two of them on fire, the statement said.

Images published on social media showed posters left on police vehicles signed "CJNG" -- the initials of the Jalisco New Generation Cartel. Reuters cited a state official as confirming the authenticity of the photos, which also showed warnings to police not to support rival crime gangs in the area.

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