Border Patrol agents detained 30 undocumented immigrants Saturday in San Diego County on suspicion of illegally entering the country using a hidden underground tunnel.
The agents discovered the tunnel after they found “23 Chinese nationals and seven Mexican nationals who had apparently just been smuggled into the U.S. through the passageway,” Ralph DeSio, a spokesperson for U.S. Customs and Border Protections, told HuffPost.
NBC San Diego reports that the tunnel, which let out at the Otay Mesa Port of Entry in San Diego County, began in a building in Tijuana, Mexico.
DeSio said that while underground tunnels aren’t new along that part of the border, they’re “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,” he added.
The San Diego Tunnel Task Force is coordinating with Mexican authorities to investigate the tunnel, which authorities suspect might be an extension of an incomplete tunnel that had been previously seized by Mexican authorities.
- This article originally appeared on HuffPost.