U.S. Border Patrol agents are confronting a dangerous, subterranean smuggling route beneath El Paso, Texas, describing the extensive storm drain system as 'a city underneath our city' that cartels exploit to move migrants from Mexico into the United States.

Agents from the El Paso Sector’s elite Confined Space Entry Team (CSET) have been granted rare access to these tunnels, navigating the hot, dark, and confined spaces where smugglers continue to seek vulnerabilities. Despite historically low levels of illegal crossings and apprehensions, the cartels are charging migrants premium fees, ranging from $20,000 to $30,000 per person, for passage through these dangerous routes.

The underground network spans miles beneath El Paso, with Border Patrol identifying 32 known entry points from the Rio Grande. Hundreds of exit points are scattered throughout neighborhoods, parks, and commercial areas, posing a security concern as smugglers and migrants can emerge in unexpected locations, including school grounds.

"There are exit points into schools, into elementary schools, where we sleep, where we play," Jason Hartman, leader of the CSET, told Fox News. "At any point, you can have smugglers or bad guys coming up in your backyard, in your playgrounds, in your kids’ schools."

Evidence of previous passages, such as abandoned tools and personal items, is often found near storm drain entrances along the Rio Grande. Border Patrol agents employ technology to monitor movement within the underground system and at exit points. For the current fiscal year, agents have apprehended 161 individuals who utilized the storm drain system. During peak migration periods, agents encountered large groups of up to 70 migrants in the tunnels, a number that has since decreased to groups of two or three.

Agents on the CSET undergo rigorous training in replica storm drains to prepare for the hazardous conditions, including monitoring oxygen levels that can fluctuate unpredictably. The physical toll of navigating the tunnels, marked by extreme heat and limited air quality, is significant even before any encounter with smugglers.

"Cartels are desperate to try to get people in," said Hamid Nikseresht, a U.S. Border Patrol Special Operations supervisor. "They’re desperate to try to fund the networks globally that they fund because this isn’t just a localized issue. This is a global issue."