LYNDEN, Wash. - The loads of dirt coming out of the windowless hut perplexed Canadian border guards. So did the loads of construction materials going in.
Acting on a hunch that the activity wasn't legitimate, the guards early this year tipped off Canadian drug investigators, who found the hut was the starting point of a well-lit, well-ventilated tunnel being built under a highway to a house in a wooded area south of the border.
Canadian and American authorities monitored the construction and, on Wednesday, shut the tunnel down, three weeks after it was completed. Five people have been arrested, the U.S. Attorney's Office in Seattle said Thursday.
It is the first tunnel discovered beneath the U.S.-Canadian border, though nearly three dozen have been found at the Mexican border, authorities said.
Reinforced with lumber, concrete and iron bars, the tunnel is 360 feet long, runs 3 feet to 10 feet below ground, and is about 4 feet wide and 4 feet tall. It's just a short walk east of the Lynden border crossing, about 90 miles north of Seattle.
"They were smart enough to build a sophisticated tunnel," said U.S. Attorney John McKay. "They weren't smart enough to not get caught."
Authorities let the tunnel remain open briefly in hopes of building a stronger case. But they insist it was under 24-hour surveillance, and that the few people who came through - some pulling hockey bags full of marijuana - were tracked.
Greg Gassett, a Drug Enforcement Administration agent based in Seattle, said that on July 16, a Twin Falls, Idaho, woman was arrested in Ellensburg, driving a car packed with 93 pounds of pot that had come through the tunnel. The Washington State Patrol also arrested a Renton man pulled over in Enumclaw with 110 pounds of marijuana, he said. Their identities were not released.
"We were in there before it was completed. There was not a day they did anything that we weren't assessing them," Gassett said.
The other three arrests were made at the house on the U.S. side Wednesday afternoon. Francis Devandra Raj, 30; Timothy Woo, 34; and Jonathan Valenzuela, 27, all of Surrey, British Columbia, made their initial appearance in U.S. District Court in Seattle on Thursday. They did not enter pleas. A detention hearing is set for July 26.
Raj owns the property where the tunnel was hidden beneath the quonset hut, authorities said. Woo was a fugitive in a 1999 marijuana case out of Seattle.
Authorities are still looking for the owner of the American house, identified in property records as a three-bedroom home built in 1979.
"We know who that individual is. We are very interested in speaking with him," McKay said.
Investigators used a "sneak-and-peak" warrant available under the USA Patriot Act to enter the U.S. house on July 2 and later installed cameras and listening devices in the home to monitor activities.