At least seven suspected gunmen died in a shootout with soldiers in Ciudad Victoria, the capital of the northeastern Mexican state of Tamaulipas, officials said.
The shootout started around 6:30 p.m. Monday when soldiers encountered a group of gunmen traveling in three vehicles, a Tamaulipas government official told Efe.
Seven bodies were found at the scene and unofficial reports said one of the dead gunmen may be Carlos Barriento, who was in charge of drug sales in the area for the Los Zetas cartel.
Army troops cordoned off the area to allow investigators to gather evidence.
The army is carrying out "Operation Northeast" in the states of Nuevo Leon, Tamaulipas, Coahuila and San Luis Potosi in an effort to weaken the drug cartels that operate in the region.
The Gulf drug cartel has been waging a war in northeastern Mexico against Los Zetas, a band of army special forces deserters turned hired guns and drug traffickers.
After several years as the armed wing of the Gulf cartel, Los Zetas went into the drug business on their own account and now control several lucrative territories.
More than 50,000 people, according to official figures, have died in drug-related violence in Mexico since late 2006, when President Felipe Calderon took office and declared war on the country's powerful drug cartels.
Calderon has deployed tens of thousands of soldiers and Federal Police officers across the country to combat drug cartels and other criminal organizations.
The use of the armed forces to fight drug traffickers, however, has failed to stem the violence.
Mexico registered 27,199 murders in 2011, or 24 per 100,000 people, the highest number since Calderon took office, the National Institute of Statistics and Geography, or INEGI, said in a report released on Aug. 20.
The Movement for Peace with Justice and Dignity, which was founded by human rights activist and poet Javier Sicilia, puts the death toll from Mexico's drug war at 70,000. EFE