Police investigating suspicious activity at a home just south of the U.S.-Mexican border found a group of men digging a secret tunnel to the United States — complete with lights, an elevator and air-conditioning.

Acting on a reports of armed men outside, cops raided the house in the border city of Mexicali and found eight workers 20 feet underground digging a tunnel with picks and shovels, according to Baja California state police spokesman Agustin Perez.

The narrow passage — only about 3 feet wide and 3 feet high — stretched some 100 yards toward Calexico, Calif. But the tunnel still had another 100 yards or so to go until it reached the U.S, Perez said.

The sophisticated tunnel is one of 70 discovered since 2000.

Another police official, Juan Manuel Guillen, told KSWT.com that police searching the home found a .38 special revolver, digging tools and a Ford F-350 truck that was used to remove the dirt.

The eight suspects, ranging in age from 27 to 52, were taken into custody. It is not known who they were working for.

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The Associated Press contributed to this report.