Eight people were gunned down in Monterrey, the capital of the northern Mexican state of Nuevo Leon, in drug-related shootings, the State Investigations Agency, or AEI, said.
Gunmen killed seven taxi drivers on Tuesday in Benito Juarez, a city in the eastern part of the Monterrey metropolitan area, the AEI said.
The gunmen were in a four-vehicle convoy and used large-caliber weapons to kill the taxi drivers, an AEI spokesman told Efe.
Some of the taxi drivers tried to flee on foot and others attempted to drive away from the scene, but they were all caught and shot in different places, the AEI spokesman said.
Police, meanwhile, found the body of a woman who had been shot multiple times in the Kalos Industrial Park in the neighboring city of Guadalupe.
The woman was kidnapped and later shot by drug cartel enforcers, police said.
The gunmen spray-painted the letters "CDG," the Spanish acronym for Gulf cartel, on the wall of a business at the industrial park, police said.
The shootings of the taxi drivers and the woman's murder may be linked because she was abducted in Benito Juarez, where the taxi drivers were murdered, police said.
The cities of Benito Juarez and Cadereyta are refuges and operations centers for Los Zetas, considered Mexico's most violent criminal organization.
The Los Zetas cartel has been battling the Gulf cartel for control of the Monterrey metropolitan area and smuggling routes into the United States.
Heriberto Lazcano Lazcano, known as "El Lazca," deserted from the Mexican army in 1999 and formed Los Zetas with three other soldiers, all members of an elite special operations unit, becoming the armed wing of the Gulf drug cartel.
After several years on the payroll of the Gulf cartel, Los Zetas, considered Mexico's most violent criminal organization, went into the drug business on their own account and now control several lucrative territories.
The wave of drug-related violence in Nuevo Leon claimed the lives of 2,003 people in 2011, official figures show. EFE