The Mexican army have found an auto shop used to bulletproof vehicles for drug gangs.
Ten people were arrested and soldiers confiscated 10 cars or SUVs that were being bulletproofed, as well as six other vehicles in a warehouse in the northern state of Sinaloa, said the army in a late-Monday statement.
Authorities did not say which cartel managed the shop, but it was in the home state of Mexico's most-wanted drug lord Joaquin Guzman, who is known as "El Chapo."
In border states such as Tamaulipas, soldiers have raided similar bulletproofing auto shops and found freight trucks completely covered in steel.
The army's operation in Sinaloa took place Sunday.
In Acapulco, federal police caught a young woman and a young man as they were getting off a car near a shopping mall with an ice chest, and inside a decapitated head and other human remains, authorities said Tuesday. Police followed them because the car matched the description in a kidnapping report.
Inside their vehicle, police found another head inside another ice chest and poster boards. When drug gangs commit crimes, they often leave messages against rival groups.
Federal police said 19-year-old Damaris Gomez, or "Guera" a nickname for blonde, is the leader of a hitmen cell working for "the street sweeper" gang. The 21-year-old man riding with her is an alleged hitmen, police said.
The local gang is fighting against the Independent Cartel of Acapulco for control of the coastal city following the 2010 arrest of a suspected drug capo for the Beltran Leyva cartel, Edgar Valdez Villarreal, also known as "La Barbie."
In the northern border city of Ciudad Juarez, across from El Paso, Texas, police found the dismembered bodies of four men in bits scattered around the city.
Prosecutors spokesman Arturo Sandoval said police first found two heads and parts of two bodies at street corner in the southern part of the city, along with a handwritten message saying "To the New Juarez cartel, keep recruiting, we're waiting for you."
The New Juarez Cartel is a group that recently appeared, and which accuses authorities of favoring the Sinaloa cartel, which is fighting a bloody turf battle against local gangs for control of Ciudad Juarez.
The other victims' remains were found scattered elsewhere in the city later in the day.
Amid continuing reports about the operation of U.S. intelligence officers in Mexico, the U.S. Embassy in Mexico City issued a statement Tuesday saying that "in accordance with Mexican law, the U.S. government does not carry out law enforcement operations in Mexico. That is a job for Mexican authorities."
The U.S. statement noted that "we closely cooperate with Mexican authorities in that effort, in full respect for Mexico's sovereignty and Mexican law, for the mutual benefit of our two counties and our shared goals. The U.S. government does this by providing equipment and training, and by sharing information."