The cramped and wandering tunnel, which connected two homes on opposite sides of the border had no ventilation, but it was outfitted with lights and at least one drainage pump, officials from Immigration and Customs Enforcement and the Drug Enforcement Administration said at a news conference here. It was thought to have been intended for drug smuggling.
State police from Sonora, Mexico, arrested five people in the house on the Mexican side of the border, where the digging was initiated, said Terry E. Kirkpatrick, acting assistant agent in charge for the drug enforcement agency. The house on the United States side was under rental but not occupied, he said.
Acting on intelligence tips, American agents had been watching the two houses since April 17. No smuggling had been done through the tunnel, Mr. Kirkpatrick said.
The dilapidated white brick house on the American side is less than half a mile from the Nogales border crossing and about 50 yards north of the 20-foot-tall metal fence that separates this sparsely populated town from its namesake in Mexico.
Mr. Kirkpatrick noted that the tunnel did not use the network of storm drainage pipes that smugglers have dug into in the past. He said its crude construction revealed a new strategy by drug smugglers. “They’re trying to just hurry up and get the things dug,” he said.
David J. Petersmarck, supervisor of special agents for Immigration and Customs Enforcement, said a circular saw with a concrete-cutting blade and picks were found near the tunnel’s opening inside the house on the American side. Mr. Petersmarck, one of the federal agents who crawled into the tunnel, said he was barely able to squeeze his shoulders down the vertical shaft.
Agents said intelligence about the tunnel’s builders and the characteristics of the hole itself indicated that the intended use was to traffic drugs, not humans.
“Once we looked at it, it was clear the tunnel would not support human smuggling,” said Anthony J. Coulson, special agent in charge for the Phoenix office of the drug enforcement agency.
Mexican state police officers who crawled into the tunnel from the Mexican side reported that it turned and twisted for more than 600 feet, American agents said. They said the tunnel was “one of the most extensive” discovered under the Mexican border since a large tunnel found south of San Diego in January 2006.
Although two neighboring houses stood less than 15 feet from the tunnel house on the American side of the border, and the tunnel traversed underneath a house immediately south, neighbors did not report hearing work, Mr. Petersmarck said, even though the digging was most likely done at night and with jackhammers.
After the search, Mr. Petersmarck and other agents sealed the entrance with plywood and about 20 bags of ready-mix concrete. It is not known whether the tunnel has been sealed on the Mexican side of the border, Mr. Petersmarck said. The long-term plan for the tunnel is to open it from the surface and fill the cavity completely, he said.
