Aug. 27 (UPI) -- Border Patrol agents in San Diego said the arrests of 30 people in the country illegally led to the discovery of a cross-border smuggling tunnel.
U.S. Customs and Border Protection said the Border Patrol agents arrested the 30 people -- 23 Chinese nationals and seven Mexican nationals -- around 1:12 a.m. Saturday near the Otay Mesa port of entry.
CBP said the people appeared to have just been smuggled into the United States, leading the agents to perform a search of the area and discover a crude opening in the ground with a ladder leading downward.
The opening turned out to be a smuggling tunnel with an exit just north of the secondary fence near the Otay Mesa port of entry.
The San Diego Tunnel Task Force, led by U.S. Immigration and Customs Enforcement's Homeland Security Investigations, was summoned to the scene and an investigation is ongoing. They are coordinating with authorities on the other side of the tunnel in Mexico, CPB said.
"While subterranean tunnels are not a new occurrence along the California-Mexico border, they are more commonly utilized by transnational criminal organizations to smuggle narcotics. However, as this case demonstrates, law enforcement has also identified instances where such tunnels were used to facilitate human smuggling," CBP said in a statement.
Investigators said the initial probe suggests the tunnel might be an extension of an incomplete tunnel that was previously seized by Mexican authorities.
The 30 people, 25 men and five women, are in Border Patrol custody pending further questioning, investigators said.