A 400-foot tunnel has been discovered along the U.S.-Mexico border that was likely used to funnel drugs between the two countries, authorities said Monday.

The secret passage connected a home in Calexico, Calif. to another house 400 feet away in Mexicali, Mexico, federal officials said. The tunnel was about 20 feet underground and was equipped with lighting and supported by wooden beams.

"Today's discovery is yet more evidence of the desperation that drug traffickers are feeling as law enforcement efforts continue to impede the flow of drugs into the U.S.," said John Fernandes, a special agent in charge with the Drug Enforcement Administration.

It wasn't immediately known whether anyone was arrested or who was responsible for the tunnel.

"This is clearly not the effort of one person," Fernandes said.

Authorities have discovered at least 39 secret tunnels on the U.S.-Mexico border since Sept. 11, 2001, the vast majority in and around San Diego and Nogales, Ariz., according to U.S. Sen. Dianne Feinstein's office.