A people smuggler has admitted to helping seven immigrants enter the United States from Mexico by traveling through sewer pipes that cross the border, prosecutors said Thursday.

Kevin Noe Campos Villa, 20, from Tijuana, Mexico, pleaded guilty in federal court to smuggling people across the border in return for $6,000. He will be sentenced in June and faces up to 10 years in prison and a potential $250,000 fine.

The court heard that Campos and three of the migrants who crossed the border under his guidance on Jan. 22 were approached by Border Patrol agents, who spotted them going through pipes 2 miles west of the San Ysidro Port of Entry.

“According to court records, two of the unauthorized immigrants who were rescued stated that they feared for their lives when crossing the river because they did not know how to swim,” the U.S. Attorney for the Southern District of California said in a statement.

One migrant told authorities that he was “swept away by the river’s current and was able to grab and hold onto a tree branch until his rescue,” the statement said.

Sewer pipes that connect the U.S. and Mexico are fitted with grates to stop people going through them — but these are opened during heavy rain to allow greater water flow without damaging the grates.

Smugglers have used the pipes for years causing U.S. authorities to warn of the dangers of entering the pipes, including not only the rushing water but its toxic content.

In a plea agreement, Campos accepted that he had been working for smugglers by building ladders to get people across the border.

“This case is yet another example of transnational smuggling organizations placing profits over safety,” said U.S. Attorney Tara McGrath in the statement.

“This is an important reminder that safety is of little concern to transnational criminal organizations,” said Chief Patrol Agent Patricia McGurk-Daniel.

People smugglers have in the past advertised their services on Facebook for as little as $4,500 per person.