Mexico sent hundreds of soldiers and federal police to a drug-violence plagued northern region Friday, the same day cartel gunmen fired on a military convoy with a grenade launcher and hit a bus carrying employees of a U.S.-owned assembly plant.
The attack on the army convoy underscored the growing boldness of Mexico's drug cartels.
The army said attackers believed to be working for the Zetas cartel opened fire on the army vehicles with guns and a grenade launcher from a highway overpass on the outskirts of the northern city of Monterrey. One soldier and five people in passing vehicles were wounded, and one attacker was killed, the Defense Department said.
The statement said the bus hit in the attack was transporting employees of the Montoi company, a branch of U.S.-based toy maker Mattel Inc. It was not clear if company employees were among the injured.
As the attackers fled in several vehicles, soldiers pursued and killed one suspect and captured two others, one of them a woman who was wounded in the gunfight, the military said.
The army said it found grenades, guns and hats with the letter "Z" _ the Zetas symbol _ at the scene as well as people who had apparently been kidnapped by the gang.
In a response to stepped-up cartel violence in northern Mexico, the government sent additional forces to the Comarca Lagunera region that straddles Coahuila and Durango states, to the west of Monterrey, the Interior Department said.
The announcement came three days after Interior Secretary Francisco Blake met with the governors of the two states. He discussed the possibility of sending federal forces to the region but also urged the governors to step up efforts to root out corruption in state and municipal police forces.
The troops and federal police are being deployed because of "weak local governments and a rise in crime including kidnapping, extortion and homicide," the statement said.
Amid relentless cartel violence, President Felipe Calderon's government has increasingly criticized state governments for failing to clean up own police forces. State government officials routinely insist organized crime is a federal offense and say state and municipal police forces are ill-equipped to confront the cartels' heavily armed gunmen.
The statement did not say how many soldiers and police are being deployed, but an Interior Department official said it will be hundreds. The official insisted on speaking anonymously because he revealed the information before the official announcement was made.
Local businessmen demanded stepped up security in the region after a prominent rancher with ties to the Lala dairy company was killed.
The region is a stronghold of the powerful Sinaloa cartel, which is fighting the Zetas cartel there.
Farther south in Durango state's capital, also called Durango, authorities said Friday they had recovered 11 more bodies at a series of mass grave pits, bringing the total number of bodies found in a monthlong search of the pits to at least 157.
The pits are believed to hold the remains of drug cartel victims, possibly including executed rivals.
Calderon has deployed more than 45,000 federal troops and police to drug trafficking hotspots across Mexico since taking office in December 2006.
Although an unprecedented number of cartel bosses have been captured or killed, violence has soared, claiming more than 34,600 lives the last four years.
The deployment of thousands of federal personnel _ first troops, then police _ failed to curb violence in the border city of Ciudad Juarez, where more than 3,000 people were slain last year.
The government said it stepped up security in the northeastern state of Tamaulipas after 72 Central American and South American migrants were slaughtered there last August, apparently by Zetas gunmen who tried to recruit them.
Despite the claim of increased security, the same cartel was accused of an even larger slaughter this year: 183 bodies were pulled from clandestine graves last month in the same area where the migrants were massacred. Many of the victims had apparently been pulled off passenger buses by Zetas gunmen trying to recruit them.
The government, however, says federal forces have also rescued dozens of kidnapped migrants in Tamaulipas in recent weeks.
On Friday, the federal Attorney General's Office announced the arrest of four municipal police for allegedly participating in the kidnapping of 68 migrants who were rescued by federal police last month from a house in Reynosa, a city across the border from McAllen, Texas.