By ARTHUR H. ROTSTEIN
Associated Press Writer

NOGALES, Ariz. (AP) - U.S. and Mexican law enforcement agents executing simultaneous raids discovered a recently completed smuggling tunnel linking the two countries, officials said Friday.

The entrances to the tunnel, described as a passageway its builders planned to use to smuggle drugs, were discovered in a home in Nogales, Ariz., and an apartment in Nogales, Mexico, according to U.S. Immigration and Customs Enforcement officials.

Five people were arrested during the raid on the Mexican location. No arrests had yet been made on the U.S. side of the border.

Investigators tipped to the tunnel’s existence during its construction have had it under surveillance since April, and no drugs were moved through it before authorities moved in, said Terry Kirkpatrick, a U.S. Immigration and Customs Enforcement official.

This tunnel crossed about 100 yards as the crow flies, but was actually about 200 yards long because it meandered and dipped. The dirt walls were reinforced in areas with wooden supports and sand bags and had a lighting system, but no ventilation.

Of more than 20 tunnels that have been found in Nogales, only about four, including the latest, have not been tied into the drainage system that runs cross-border beneath Nogales, Mexico, and Nogales, Ariz.

“To have a fully serviced independent tunnel absent using the drainage system under these two cities is a significant event for us,” said Tony Coulson, assistant special agent in charge for the Drug Enforcement Administration in Arizona.

Agents who served a search warrant late Thursday at the tiny, one- story home found the tunnel entrance hidden beneath plywood sheets weighted down with bags of dirt inside a utility room.

The home was largely unfurnished, and searchers found picks, a jackhammer and other excavation equipment.

The tunnel was the largest discovered along the U.S.-Mexico border since January 2006, when a tunnel extending nearly a half-mile from San Diego to Tijuana was found.

Federal officials said the tunnel discovered Thursday has been temporarily sealed and will be filled in after the investigation is complete.