A Mexican citizen was arrested on drug charges in the investigation into the longest cross-border tunnel ever found along the U.S.-Mexico border, U.S. officials said Monday.

The suspect, whose identity was not immediately released, was taken into custody during the weekend by U.S. Immigration and Customs Enforcement agents.

He was expected to be arraigned Monday on charges of conspiracy to import a controlled substance.

The 2,400-foot-long tunnel runs from a warehouse near the airport in Tijuana to a warehouse in San Diego. It was unclear how long it had been in operation, but more than 2 tons of marijuana were found inside.

Authorities said the tunnel was five feet high and as deep as 90 feet below the surface. It had a cement-lined floor, lights that ran down one of the hard soil walls, and a groundwater pump and pipes the circulated fresh air.

The allegations against the Mexican man stemmed from his connection to the U.S. warehouse, which was operated by V&F Distributors LLC, ICE said in the news release Monday announcing the arrest.

The company, which incorporated last year in California, paid $2 million to lease the 49,377-square-foot commercial warehouse for five years with the stated purpose of distributing produce, according to real estate records.

On Friday, immigration authorities warned it had received intelligence that the Mexican drug cartel behind the tunnel had threatened the lives of people who had used it as well as the lives of those involved in the passageway's design or construction. ICE appealed to those people to seek out U.S. immigration agents at Mexican border crossings and pledged to do everything possible to protect them.

The Drug Enforcement Administration has said it suspects Tijuana's ruthless Arellano-Felix drug syndicate or another well-known cartel was involved.