Armed with automatic weapons, soldiers wearing ski masks to shield their identities searched vehicles for signs of drug smuggling after the government ordered 5,500 troops to deploy to the area by land, sea and air in the marijuana-growing region, also the President's home state.

The surge, one of the biggest in the three-year drug war, came after drug gangs targeted federal police following the capture of a high-ranking member of the local La Familia cartel.

Last week members of the cartel dumped the tortured and blood-smeared bodies of 12 federal police in a heap by a remote highway - the latest victims in the violent war that has killed over 12,800 people since President Felipe Calderon came to power in 2006.

A horrific film allegedly showing the policemen being stripped, beaten and executed was briefly posted on YouTube, the El Universal newspaper reported.

Ten municipal police officers from Michoacan were being held in custody on Saturday, suspected of collaborating with the cartel in the murders, the Mexican attorney general's office said.

The state has become the epicentre of the country's drug war, and residents in the regional capital Morelia told how local forces had reached their limits.

Last September suspected drug gang hit men threw two grenades into a packed crowd celebrating Mexico's independence day.

'We've reached a point where the local authorities are tapped out, and so unfortunately it's necessary to call in extra forces to try and restore the peace to Michoacan,' said Gerardo Gomez, a Morelia resident.

The large deployment of troops comes less than five months after a similar effort to rid Ciudad Juarez of drug gangs.

Nearly 2,000 soldiers and armed federal police poured into the city, located just across the border from El Paso in Texas. The surge, in early March, was in response to the murder of 250 people by hitmen fighting for lucrative smuggling routes.

LA FAMILIA AND THE MEXICAN DRUG WAR

The infamous cartel La Familia has grown in strength to the point where it controls elements of local police and even politicians in Michoacan, which has become the epicentre for violence in a raging drug war.

Mexico's President Calderon hails from the state, which is home to sparsely inhabited mountains hiding drug farms and labs.

The recent wave of revenge attacks on security forces indicates that La Familia - which is battling a Gulf Cartel known as the Zetas for control of Michoacan - has been little weakened by the military crackdown.

La Familia appears to have gained enormous power in the state. In May, troops rounded up ten mayors and a string of police chiefs accused of working for the cartel.

The cartel follows a code of conduct that bars its members from taking drugs or drinking alcohol and claims that its aim is to protect Michoacan from Zeta hit men.