"We've gotten all the necessary evidence we need," said Rodney Benson, a special agent in charge of the Seattle division of the U.S. Drug Enforcement Administration.

The tunnel, which linked a storage warehouse in Canada with a vacant home in Lynden was raided and shut down by agents last month. Itwas the first drug smuggling tunnel discovered underneath the northern border.

Five people have been arrested and face marijuana charges.

The demolition planned for Thursday and Friday on the U.S. portion of the tunnel will involve cutting through the road above the tunnel and removing most of the 1,000 wooden supports inside

After that, cement barriers will be placed at the tunnel entrance near the Lynden home and underground at the border. The tunnel will then be filled with dirt, gravel and a special type of liquid foam cement.

Canadian authorities have already closed up their side.

Federal agents in Seattle say the tunnel is one of the most sophisticated operations they've seen. It was about 4 feet wide, 4 feet high and was equipped with electricity and a ventilation system.