No contraband was found in connection with the tunnels, which linked warehouses in Tijuana, Mexico, with warehouses in an industrial park in the Otay Mesa area of San Diego, according to a statement from U.S. Immigration and Customs Enforcement's Homeland Security Investigations.
The first tunnel, stretching about 600 yards, was discovered Tuesday. It was described as being equipped with lighting, a crude rail system and wooden trusses. The entrance on the U.S. side is inside a warehouse where a cement cap covered a 70-foot shaft. A pulley system was installed to hoist goods into the building, which was filled with children's toys and boxes of televisions.
The other tunnel, located Thursday, stretches more than 700 yards and was built with more sophisticated features including a multi-tiered electric rail system and ventilation equipment.
On Wednesday, investigators with the San Diego Tunnel Task Force arrested a 73-year-old woman from the San Diego suburb of Chula Vista for investigation of overseeing the logistics at the location of the first tunnel. Her name was not immediately released.
The tunnels were the sixth and seventh found in the area in less than four years, ICE said.
"Here we are again, foiling cartel plans to sneak millions of dollars of illegal drugs through secret passageways that cost millions of dollars to build," U.S. Attorney Laura Duffy said in a statement. "Going underground is not a good business plan."
Other participants in the investigation include U.S. Customs and Border Protection and the Drug Enforcement Administration.