MEXICO CITY (AP) — Twelve people were killed in a series of coordinated and near-simultaneous attacks in the violence-wracked city of Salamanca, authorities in the central Mexican state of Guanajuato said Friday.

The victims were found Thursday at multiple points across the refinery city of over 200,000. In at least one case, a banner signed by a drug cartel was left with some of the bodies.

The massacre is the latest episode in a wave of violence in Salamanca, west of the state’s capital Guanajuato, where gunmen killed four men and wounded two others in an attack at a drug rehabilitation center late Tuesday.

Authorities said there are no clear suspects and they continue to investigate.

The industrial and agricultural state of Guanajuato has for years been the scene of a bloody turf battle between the Jalisco New Generation Cartel and a local gang, the Santa Rosa de Lima Cartel. Guanajuato has the highest number of homicides of any state in Mexico.

Security analyst David Saucedo said that the Jalisco New Generation Cartel has control of urban areas, while Santa Rosa de Lima controls rural ones, but they continue to fight for control of cities like Salamanca.

“There’s been a presence of the National Guard but (the violence) hasn’t stopped,” he said. “Salamanca has a very complicated situation.”

Saucedo said that Salamanca has had three different police directors in the last three years, noting a lack of capability to take on the organized crime groups.

Salamanca Mayor César Prieto Gallardo was quoted in the media as saying that city and state authorities are working in a coordinated manner. “Unfortunately," he said, "This is a conflict between delinquent groups. The civil population has nothing to do with this.”

____

Follow AP’s coverage of Latin America and the Caribbean at https://apnews.com/hub/latin-america