MEXICO CITY, MEXICO - Six heads of police officers were found in plastic bags in northern Mexico, while their bodies were still missing, a justice official said Wednesday.

The gruesome discovery came amid a police and military clampdown on violent drug gangs blamed for the deaths of more than 14,000 people across Mexico in the past three years.

'Six human heads were found in plastic bags in a garden in the town of Cuencame (in northern Durango state),' a spokesman for the state attorney general's office told AFP, requesting anonymity.

The six were police officers from the State Agency of Investigations who were reported missing on Tuesday, the spokesman said.

Violence has risen despite the deployment of some 50,000 security forces across the country to take on its powerful drug gangs.

Durango is in an area known as the 'Golden Triangle,' a flashpoint in drug trafficking activity and violence, which also includes the northern states of Chihuahua and Sinaloa.