Marines rescued 13 people apparently being held hostage and arrested 10 suspected members of the Gulf drug cartel in Nuevo Laredo, a border city in the northeastern Mexican state of Tamaulipas, the Navy Secretariat said.
The operation took place on June 1 and was "derived from a tip from a citizen, who reported the presence of armed people at a house in the city," the secretariat said.
The suspects told investigators that they belonged to the Gulf cartel, one of Mexico's largest criminal organizations.
Marines seized 17 AK-47 assault rifles, two grenade launchers, a machine gun and six pistols from the suspects, the secretariat said.
The suspects also had 25 hand grenades, 241 ammunition clips and 16,500 rounds of ammunition, as well as two automobiles and communications equipment, in their possession, the secretariat said.
The Siedo organized crime unit of the Attorney General's Office will conduct the investigation.
Nuevo Laredo, located across the Rio Grande from Laredo, Texas, is considered a stronghold of the Los Zetas drug cartel, which was founded in 1999 by Heriberto Lazcano Lazcano, known as "El Lazca," and three other army deserters, all members of an elite special operations unit.
The violence has surged in recent months in Nuevo Laredo, where the army has been responsible for public safety since last year due to the rampant corruption in the police department.
The violence in the border city is being blamed on a war between Los Zetas and the Gulf cartel.
Media reports say the Sinaloa and Gulf cartels have formed an alliance to fight Los Zetas.
There are reports that gunmen from the Sinaloa cartel arrived in the border city a few weeks ago to help the Gulf organization gain control of the area.
Los Zetas started out as the armed wing of the Gulf cartel, but the two criminal organizations later had a falling out.
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.
President Felipe Calderon declared war on Mexico's drug cartels shortly after taking office in December 2006.
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.
Unofficial tallies put the death toll from Mexico's drug war at more than 50,000. EFE