SAN DIEGO -- Crews in rural East County have begun destroying a cross-border tunnel that authorities say was used by associates of the Arellano Felix drug cartel to smuggle marijuana and cocaine into the United States.

Drug Enforcement Agents, acting on an anonymous tip, found the tunnel Feb. 27 while executing a search warrant at a house about 60 miles east of San Diego in the U.S. community of Tierra del Sol near Boulevard.

A construction crew Thursday began pouring concrete into the U.S. portion of the 1,000-foot tunnel.

The tunnel, which is wood-framed and equipped with electric lights and a ventilation system, begins in Mexico on the outskirts of Tecate under a fireplace in a ranch house located about 200 feet from the border fence.

Its opening on the U.S. side of the border is in an unoccupied two-story house. The home's owner is not believed to be involved in drug smuggling and apparently had no knowledge of the tunnel's existence, authorities said.

Agents found 500 pounds of marijuana near the entrance of the tunnel when they entered it, and said it likely was also used to bring cocaine into this country.

Authorities believe the tunnel has been in place for several years and whoever used it was associated with the Arellano Felix cartel.

"For them to use this tunnel, it had to be under the control of the Arellano Felix organization," Errol Chavez, special agent in charge of the DEA in San Diego, told reporters shortly after the tunnel was discovered.

The Arellano Felix group is said to be one of the most powerful and well-organized drug trafficking cartels operating in Mexico. Its members are known to use planes, boats and tunnels to move drugs.

Since the tunnel's discovery, one of the cartel's leaders has been arrested and another killed.