Mexico City – Thirteen people, including a marine, died in a shootout around the Falcon Reservoir near the U.S. border in Tamaulipas state, the navy said Monday.
The shootout, in which army troops also participated, occurred on Sunday.
The marines "repelled an armed attack by members of an organized crime group," the navy said.
The shootout started when marines patrolling an island in the Falcon Reservoir, located about 3.5 kilometers (2.1 miles) northeast of the town of Nueva Ciudad Guerrero, found "a camp presumably belonging to the Los Zetas criminal organization," the navy said.
The Zetas gunmen immediately opened fire on the marines, the navy said.
The marines took control of the camp and seized 19 rifles, a .50-caliber Barrett rifle, a machine gun and "ammunition and ammunition clips for different firearms," the navy said.
"The camp was used as a point of departure for marijuana being transported on speedboats to the United States," the navy said.
Army troops deployed in Nueva Ciudad Guerrero provided support to the marines.
Zapata, Texas, is the largest city on the U.S. side of the Falcon Reservoir.
David Hartley, an American citizen, disappeared on Falcon Lake last September after being attacked by suspected drug traffickers.
The search for Hartley's body was suspended on Oct. 14 by Tamaulipas state officials.
Hartley and his wife, Tiffany, who lived in McAllen, Texas, were riding jet skis on Sept. 30 at the reservoir when they were attacked and chased by men aboard a boat, the victim's wife told police.
Hartley was shot in the head, Tiffany Hartley, who managed to escape to Texas, said.
Texas Gov. Rick Perry has called on Mexican officials to press on with the investigation, which has not yielded any arrests.
A Mexican police investigator working on the Hartley case was murdered and decapitated.
Rolando Flores Villegas, who was in command of the police unit in the city of Miguel Aleman, was working on the operation to recover the U.S. citizen's body on the Mexican side of the lake.
Mexico used trained searchers, boats and helicopters to look for Hartley's body in the Falcon International Reservoir, officials said.
The search got off to a slow start because Mexican police initially doubted Tiffany Hartley's story and did little to recover her husband's body, U.S. media reported.
The Falcon Reservoir is located in Tamaulipas, where the Gulf and Los Zetas drug cartels have been battling for control of smuggling routes into the United States.
About 40,000 people have died in drug-related violence since President Felipe Calderon declared war on Mexico's cartels shortly after taking office in December 2006.