WATCH: Inside look at the dangerous cartel human smuggling tunnels still being used at border

Despite President Donald Trump’s tight clamp on the border, cartels are continuing to attempt to smuggle humans and narcotics by going underground using a vast network of storm drain tunnels in El Paso.

U.S. Customs and Border Protection’s (CBP) elite Confined Space Entry Team gave Fox News an exclusive look inside the narrow tunnels, which stretch for miles across the region.

There are 32 entry points into the tunnels from the Rio Grande and hundreds of exit points throughout the city. The team said this makes patrolling the tunnels a game of "whack-a-mole" because smugglers can pop out of storm drains at any point. According to CBP, it is much more difficult for Border Patrol agents to detect and intercept smugglers using these secret routes. Nevertheless, they use technology to detect movement underground, monitor entry points and strategically position teams to intercept groups.

The greatest challenge, a team member told Fox News, is the heat and the time spent in the tunnels’ thick, low-oxygen air. He said that often by the time they encounter a cartel smuggler, "you’re already exhausted, and now, you have to potentially fight with someone underground."

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"You can’t call for backup; you can’t call for help. It’s just you and your team versus everybody else," he said.

Team members said that the number of migrants being smuggled through the tunnels has dropped dramatically under Trump. Whereas there would regularly be groups of 40 to 60 people moving through the tunnels, agents now typically encounter two or three at a time.

Still, the smugglers have not stopped entirely. Reports indicate that cartels have significantly increased their fees for would-be illegal immigrants to take the tunnel routes, with migrants paying $20,000 to $30,000 per person to be guided through the underground routes.

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CBP also said that smugglers are increasingly using social media to recruit and train guides to navigate the hazardous passageways. The conditions underground are perilous, with poor air quality and intense heat, and El Paso daytime summer temperatures often exceed 100 degrees.

To prepare for this mission, the elite CBP team undergoes specialized training to operate underground, monitor oxygen levels and navigate the tunnels.

Fox News got this exclusive look as the Department of Homeland Security announced this week that June marked 14 consecutive months of zero releases at the border, continuing what it touted as an "unprecedented trend of historically low border crossings."

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Daily apprehensions at the border are down 94 percent from what they were during the Biden administration, according to DHS.

Meanwhile, CBP has broken staffing records this spring, the agency announced, reaching 21,471 agents — the most in the agency’s 102-year history.

Fox News Digital's Leo Briceno contributed to this report.