SAN DIEGO (AP) Officials say dozens of migrants fleeing from Border Patrol agents led authorities to a surprising discovery: A tunnel under the US-Mexico border in San Diego used to bring Chinese nationals illegally into the United States.
Cartels have built hundreds of tunnels to move drugs into California.
Border Patrol agent Eduardo Olmos says agents found the tunnel after chasing migrants trying to run back to it to get back to Mexico.
Authorities detained 23 Chinese nationals and seven Mexicans.
Mike Unzueta says smugglers used to avoid moving people through the tunnels because it was not worth it.
He says the discovery may indicate it is lucrative enough because Chinese nationals pay up to $20,000 each.
Unzueta is the former head of investigations at U.S. Immigration and Customs Enforcement in San Diego.