Updated

A California man pleaded guilty Monday to attempting to construct a drug-smuggling tunnel across the U.S.-Mexico border.

Habib Mujica, 35, from Calexico, Calif., was arrested in May in connection with the tunnel upon returning to the U.S. from Mexico after he spent six years in a Mexican prison for trafficking guns, the Los Angeles Times reported.

Homeland security agents found Mujica’s operation in 2011 inside a warehouse in Calexico. While he was imprisoned, Mujica reportedly told a partner to lease the warehouse and buy tunnel-building equipment like pipes, electric saws, and a forklift, according to his plea agreement. The construction of the tunnel was already underway when it was discovered, according to the U.S. Attorney’s office.

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Homeland security agents found tools inside the warehouse, which was slated to pose as a bicycle business. (U.S. Attorney's Office)

MEXICAN POLICE UNCOVER MASSIVE DRUG TUNNEL LEADING TO US

Mujica also admitted he planned to run a cover business called Baja Bikes from the location.

If convicted, Mujica could face up to 40 years in prison and up to $750,000 in fines. His sentencing has been scheduled for Nov. 27.