The Mexican government is sending 5500 troops, police and naval officers to a western state to fight a flare-up in drug gang violence.
The surge, one of the biggest in Mexico's three-year drug war, will reinforce several hundred personnel in Michoacan state, known for its cannabis crops.
The reinforcements, backed by armoured vehicles and Black Hawk helicopters, are expected to target cartel safe houses.
The move follows the discovery of the bodies of 12 federal police officers by a Michoacan mountain road last weekend. They had all been tortured and murdered - the latest of about 12,800 people killed in drug gang violence across Mexico since late 2006.
They had been ambushed by members of a drugs gang, in apparent retaliation for the capture of one of their leaders.
President Felipe Calderon has vowed to continue his war against drugs cartels and not be intimidated. Michoacan is the president's home state.