At least 18 bodies were discovered in eight pits near the town of La Barca, which lies at the border between the states of Jalisco and Michoacan, an agent from the federal prosecutor's office told AFP.
Investigators had initially found nine bodies in recent days and the last two were removed today, the agent said on condition of anonymity.
One of the victims is a woman while four of the remains were mere bones. Authorities were still combing the rural area for any other corpses today.
The state of Michoacan is a bastion of the Knights Templar drug cartel, which has been involved in turf wars against the Jalisco New Generation gang.
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The federal government has deployed thousands of troops to Michoacan to crack down on the Templars, whose reign of terror has prompted several towns to form "self-defense" vigilante groups.
Six other bodies were found on Thursday on the outskirts of the Pacific resort of Acapulco, which lies in the southwestern state of Guerrero, local officials said.
The five men and one woman were buried in a field of lime trees next to a burning car where another body was found.
More than 77,000 people have been killed in drug cartel-related violence in Mexico since 2006.