SAN DIEGO -- Investigators found two tons of marijuana at the Mexican end of a sophisticated cross-border tunnel that leads to an industrial building in Otay Mesa, it was reported Thursday.

Late Wednesday night, authorities were still pulling marijuana out of the tunnel, which is outfitted with electricity and a ventilation system, 10News reported.

"We know it's used for drug trafficking (but) obviously it's more than that. The tunnel illustrates the danger, risks, security, safety and concern to (the) American public," said John Fernandes, with the Drug Enforcement Agency.

The tunnel, discovered Wednesday, begins about 85 feet below a small warehouse about 175 yards south of the U.S. border. The other end is an apparently vacant industrial building in Otay Mesa. It is about 2,400 feet long, or about the length of eight football fields.

During a press conference Thursday, a federal official said the tunnel was the "most sophisticated" tunnel ever found in that region.

A concrete-lined shaft 6 feet by 12 feet with a metal ladder leads to the tunnel, which is tall enough for a person to stand in, the newspaper reported.

A gurney hanging from a pulley system attached to one of the warehouse's beams allowed items to be moved into and out of the tunnel. Two trucks and a van were parked inside the warehouse, according to the newspaper.

Mike Inzueta, head of Immigration and Customs Enforcement, got a chance to walk in the tunel.

"It does have a sophisticated lighting system and ventilation system to bring air into tunnel. (It) also has what we believe is a pumping system to pump ground water," said Inzueta.

Authorities said the elaborate tunnel bore the hallmarks of Mexican drug cartels, which have spent millions of dollars in the last 15 years to find a way to move contraband across the border, according to the newspaper.

Authorities did not estimate how long the tunnel might have been in use or provide information about who might own the properties where the tunnel's entrance and exit were found, the newspaper reported.

Based on tips, U.S. officials began investigating the possibility of a tunnel in the area in 2004, the Union-Tribune reported.

Border Patrol spokesman Richard Kite said a separate, smaller tunnel was discovered Wednesday morning after a Border Patrol vehicle struck a sinkhole near the San Ysidro border crossing.

The tunnel was about two feet underground. It started in a vacant lot in Tijuana and extended about 30 feet into the U.S. -- near a storm drain.

A total of four tunnels have been discovered in one month, 10News reported.

Other tunnels have been found in Arizona and between Washington and British Columbia on the Canadian border, but none have compared to this most recent tunnel.