"We believe this to be the longest tunnel that we have discovered in this district to date," said Laura Duffy, U.S. attorney for the Southern District of California.
Authorities arrested six people and seized more than 2,000 pounds of cocaine and more than 14,000 pounds of marijuana. The cocaine is valued at around $22 million.
"We believe this to be the largest single seizure of cocaine related to a tunnel in the California-Mexico border," Duffy said.
At about 3-feet wide, the tunnel measured the length of more than eight football fields (nearly a half-mile) and was equipped with lights, ventilation, a rail system and a motorized freight elevator capable of carrying up to 10 people, according to federal officials.
The six arrested in San Diego were charged with various drug trafficking and tunnel-related charges, including conspiracy to import and distribute cocaine and conspiracy to use a border tunnel.
Authorities said there have been more than a dozen secret passages found along California's border with Mexico since 2006.
In the past five years, federal authorities have detected more than 75 cross-border smuggling tunnels, most of them in California and Arizona.