() Border Patrol agents in Texas’ Rio Grande Valley sector are ramping up efforts to dismantle smuggling operations.

Human smugglers are becoming more sophisticated, agents said, using tunnels as part of a broader network of illegal entry points along the border.

spent time with the Border Patrol Marine Unit, whose agents serve as the first line of defense against illegal immigration and drug trafficking into the United States.

The area is a common route for smugglers, who use rafts to get migrants across the river and onto U.S. soil. But they’re not only using rafts agents say smugglers have also taken their operations underground.

During a recent operation along the banks of the Rio Grande, the team approached a makeshift tunnel, where smugglers had installed a pipe before agents were able to seal it off with cement.

Agents told the tunnel was only halfway completed and never fully operational but that it was just one of many, as smugglers along the border continually adapt their methods.

A drainage system that was once used by smugglers, according to Border Patrol, was blocked off by a cage placed by agents, but officials said cartel operatives are still attempting to repurpose it.

There was evidence that fresh cuts had been made clear signs of smugglers testing weak points, agents said. Alongside this system, smugglers are also reportedly digging makeshift tunnels and constantly looking for new ways to bypass security.

“Once they start digging holes like that, you gotta be extra careful and not just look at the actual drain, but look around. And that’s how we found that other one,” Cesar Hernandez of the Border Patrol Marine Unit told .

Agents later uncovered another tunnel after finding wooden planks reinforcing the walls and a wooden door, both covered with fresh brush.

Border Patrol agents said they remain vigilant while searching for tunnels along the Rio Grande because smugglers work fast. One day, the area can look untouched, they said; the next, a tunnel can be found hidden under fresh brush or debris.

The Marine Unit is one of the most dangerous jobs in Border Patrol, agents said. They told that while the job may seem quiet on the surface, the reality is far from it. Their work never stops, they said, and they remain on high alert because smugglers and cartel scouts are always watching.

Smugglers aren’t just going underground. They’re still using the river too, officials said. Even with tunnels emerging, the Rio Grande remains a critical crossing point.

On the Mexican side of the river, migrant camps that were once full now appear abandoned, reflecting a shift in enforcement.

Border Patrol is apprehending fewer migrants, and cooperation between the U.S. and Mexico is ostensibly having an impact.