Thirty undocumented immigrants suspected of trying to cross into the United States from Mexico through a hidden tunnel spanning the border were detained by authorities in San Diego early Saturday.

U.S. Customs and Border Protection (CBP) agent Eduardo Olmos told NBC 7 that U.S. Border Patrol agents spotted the large group at around 1:30 a.m. near the Otay Mesa Port of Entry in south San Diego County, near the border crossing bridge off Britannia Boulevard and Otay Pacific Drive.

Hidden Border Tunnel Found at Otay Mesa Crossing

When the suspects realized they had been seen by the agents, many of them tried to flee by going back into the mouth of a tunnel that investigators said had been constructed for the purpose of illegally smuggling undocumented immigrants from Mexico into the U.S.

Border agents followed the group and detained several on the surface of the tunnel at Drucker Lane and Siempre Viva Road; others were detained inside the tunnel, officials said.

Of those detained, 23 were Chinese nationals and seven were Mexican nationals. They are now in the custody of U.S. Border Patrol pending further questioning.

[DONT CHANGE MAIN HEADLINE] San Diego's Border Busts

According to investigators, the tunnel began in a building on Calle Mar Barmejo in the Garita de Otay area in Tijuana, approximately 328 feet south of the U.S.-Mexico border in San Diego and three miles from the border crossing bridge.

Mexican authorities are working the investigation on that side, at the building, trying to determine who is responsible for the build-out and operation of the smuggling tunnel.

On the U.S. side, at least one agent was seen Saturday manning the tunnel's exit, which was located just north of the secondary fence in the vicinity of the Otay Mesa Port of Entry. Olmos said CBP agents would stay in the area as long as needed to aid in the investigation.

As of 4 p.m., Olmos said no drugs had been discovered inside the tunnel.

Members of the San Diego Tunnel Task Force, led by U.S. Immigration and Customs Enforcement’s (ICE) Homeland Security Investigations (HSI), are currently on scene investigating.

ICE spokeswoman Virginia Kice sent this statement to NBC 7 about the tunnel, which read, in part:



"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.

The probe into the newly discovered tunnel is ongoing and members of the San Diego Tunnel Task Force are coordinating closely with their law enforcement counterparts in Mexico on the investigation. Preliminarily it appears this latest tunnel may be an extension of an incomplete tunnel previously discovered and seized by Mexican authorities."

Customs and Border Patrol officials told NBC 7 in the last two years there has been an uptick in nationals from countries other than Mexico trying to enter the country illegally.

