Acapulco, Mexico: Sixteen people were killed during Christmas holiday celebrations in Mexico’s main drug-trafficking states and six human heads were found in one location, officials said.

A gang slaughtered seven people — including three police officers — at a family celebration in the violent southern state of Guerrero, police told AFP.

The massacre occurred early Christmas Day outside a house in the village of Puente del Rey, where the gunmen shot dead the six men and one woman, aged 24 to 54.

Those killed were three brothers, their father, their uncle, and a man and a woman who had been invited to the home.

Three of the victims were police officers, a regional security ministry official said.

In Chihuahua — which borders the United States and has, like Guerrero, endured brutal drug-related violence — nine people were killed during Christmas celebrations, authorities said.

Five of them died in Ciudad Juarez, including three women who were first tortured and a man whose dismembered remains were found in an abandoned trunk.

In the western state of Michoacan six human heads were found, according to the local prosecutor’s office.

Authorities have not identified the remains, which have been transferred to a forensic office for analysis.

The heads were found near the border with Jalisco, where the powerful Jalisco Nueva Generacion cartel operates.

That gang is known for clashing with rival criminals in neighboring Michoacan state, where the Knights Templar drug cartel once held sway.

Cartels have been burying their victims in hidden graves across the country for years, and authorities regularly find human remains.

Guerrero recently earned international infamy as a region where 43 students in 2014 went missing, and were presumably murdered, at the hands of corrupt police working for criminals.

The government says that since 2006 more than 170,000 people have been killed and more than 28,000 have been reported missing. The data does not indicate which cases are related to organised crime.