Mexican authorities said on Monday they found the bodies of 12 men and women left in two abandoned vans in a rural area in the central state of San Luis Potosi, an area brimming with drug cartel activity.
The San Luis Potosi state attorney general's office said a written message from an alleged criminal organization was found next to the bodies of the 10 men and two women.
The attorney general's office did not reveal the content of the message or give details about the cause of death of the victims, who have not been identified.
Several organized crime gangs operate in the state, including the powerful Zetas and the Jalisco New Generation Cartel.
Between January and August of this year 411 people were murdered in San Luis Potosi, according to official data, a 43% increase over the same period in 2019.
Mexico's government has unsuccessfully tried for more than a decade to contain growing cartel violence with large military and police operations.