ROSARITO BEACH – The Mexican army seized nearly 7,000 pounds of marijuana Wednesday at a beach situated about 20 minutes from the city, military authorities announced.

The drug was apparently abandoned at the shore around dawn by the people who landed there when they saw Mexican soldiers. No one was detained.

Mexico's National Defense Department announced the seizure Wednesday afternoon at the Morelos military base in Tijuana. It comes a week after a cross-border sophisticated tunnel was discovered in Otay Mesa and in a year of record confiscations of marijuana and other illegal drugs in the region.

During a maritime patrol around dawn at a beach called La Burrita, the military discovered the 1,222 packages of marijuana, which weighed at total of 6,921 pounds, apparently were abandoned by smugglers, the department said.

It did not immediately attribute the drug to any specific criminal organization.

In July, the Mexican army seized 300 acres of marijuana plants south of Ensenada, considered the largest such seizure in the country.

In October, the military seized 788 pounds of cocaine, which had an estimated value of at least $11 million, said at the time Gen. Gilberto Landeros, the commander of the Second Military Zone. He said the seizure was the largest in the Baja California region.

Nearly 3,200 pounds of cocaine have been seized in the region and tens of tons of marijuana in 2011.

Most of those drugs have been linked to the Sinaloa cartel, which experts say has won control of domestic sales and smuggling to the United States in this region.

That criminal organization emerged as the victor after an internal war between the Tijuana-based Arellano cartel and a breakaway cell left 2,327 dead in the city during 2008 to 2010.

The Sinaloa cartel, bitter rivals of the Arellanos, is ushering in a new era of drug trafficking to the region, the experts say.

And that is occurring despite an orchestrated campaign by state, federal and military authorities to confront organized crime on the border.

"One cartel was dismantled but another one arrived because the demand for drugs has not changed," said Vicente Sánchez, a researcher at the Mexican think tank Colegio de la Frontera Norte. "Consumption has not fundamentally changed and that leads to cartels working in Tijuana."

omar.millan@sandiegored.com