U.S. Border Patrol agents arrested 30 people Saturday morning near the Otay Mesa port of entry in the San Diego-Tijuana area. Agents at the San Diego Sector found a California-Mexico smuggling tunnel following the multiple arrests of the people who entered the country illegally.

The U.S. agents encountered the undocumented individuals at roughly 1:00 AM. According to Customs and Border Patrol (CBP), the people were just smuggled into the United States. While searching the area, the agents discovered a rudimentary ground opening, which had a ladder inside.

The agents realized it was a smuggling tunnel, which exited slightly north of a secondary fence in the area of the Otay Mesa port of entry – one of three entries in the San Diego-Tijuana region.

Mexican and Chinese nationals detained for questioning

The 30 individuals are in Border Patrol custody. Further questioning is pending. Of the 30 people detained, seven are Mexican nationals, three women, and four men, in addition to 23 Chinese nationals, two women and 21 men. U.S. Immigration and Customs Enforcement’s (ICE) Homeland Security Investigations (HIS) are leading an on-scene investigation with members of the San Diego Tunnel Task Force.

Though it is more common for transnational criminal enterprises to use subterranean tunnels for smuggling narcotics, CBP stated that such tunnels facilitating human smuggling are also not unheard of along the border between California and Mexico.

CBP agent Eduardo Olmos stated to NBC 7 that after the suspected illegal immigrants realized that were noticed by the agents, several of the people tried fleeing to return to the opening of the tunnel. Agents followed a group of the suspects and held several on the tunnel’s surface. Additional people inside the tunnel were detained.

Steep price for illegal entry into U.S.

In recent months, the price for smuggling a person into the United States has increased dramatically, according to the Washington Times. The approximate price cited by both Mexican and Central American migrants is $10,000. Chinese migrants, according to the Times, have cited paying more than $50,000 to enter the United States.

The tunnel’s beginning point was in a building in Tijuana, roughly 328 feet south of the San Diego border between the United States and Mexico, NBC 7 reported. Mexican authorities are handling the investigation at the site of the building in Tijuana to assess who shoulders responsibility for creating the expanse of the tunnel from Mexico.

CBP stated that the tunnel preliminarily seems that it “may be an extension of an incomplete tunnel previously discovered and seized by Mexican authorities,” NBC 7 noted. In 2016, a tunnel in the same area was used to smuggle seven tons of marijuana and a ton of cocaine, Reuters reported. Federal agents said the 2016 tunnel spanned a half-mile under the border and, at the time it was unearthed, it was one of the longest in California.