EL PASO, Texas (Border Report) – Imagine a 20-year-old man sharing sleeping quarters, showers and a bathroom with boys as young as 13.

That’s a chilling scenario that worries U.S. authorities as they grapple with a flood of adult unauthorized migrants being coached by Mexican cartels to say they’re minors to avoid being sent back across the border.

U.S. Border Patrol agents in Fiscal Year 2021 unmasked 559 adult foreign citizens posing as unaccompanied children in the El Paso Sector alone. Since October 1, agents have detected another 55.

“We want to avoid putting in adults where we have children. That’s a big concern for us,” Border Patrol spokesman Fidel Baca said. “Unaccompanied children are in our custody a very limited amount of time. However, they do go on to other organizations and we want to avoid passing an adult to their custody and mixing them in with children. That’s a big red flag for us.”

The U.S. treats foreign children much differently than unauthorized single adults and the cartels know it.

Most adults are usually expelled under the Title 42 public health order within hours of entering the United States illegally. Children traveling alone are sent to a processing center in Northeast El Paso and transferred to Health and Human Services facilities within days. From there, they’re sent to family members or sponsors within weeks.

According to U.S. Customs and Border Report data, some 23,000 unaccompanied minors came through the El Paso Sector last fiscal year. A total of 14,616 came from Guatemala; 3,110 from Honduras; 2,303 from Mexico; 1,494 from El Salvador; and the remaining 1,383 were natives of other countries.

Border Patrol officials say the cartels are coaching the adults – primarily Central American males – to say they’re under 18; they provide them with fake documents, altered documents or someone else’s birth certificate, the Border Patrol has learned through interviews.

“The people we’re seeing posing as children are those we have not seen before in the United States. So, they (the cartels) know the minute we run their fingerprints they’re not going to have any previous encounter or criminal history, so it’s going to be harder for us to determine their true identity,” Baca said.

The cartels provide the fake children with equally bogus birth certificates or other documents that were genuinely issued by a foreign government but were altered to show a different name or date of birth. In some cases, these transnational criminal organizations get a hold of someone else’s real documents and just sell them to migrants who can afford to pay.

Baca said the Border Patrol and several other agencies under the umbrella of the Department of Homeland Security work closely with each other and with foreign governments to thwart the cartels’ sophisticated methods.

“We have close partnerships with the governments of Central and South America that help us look closer into those people we believe are not actually children,” Baca said.

It’s a daunting task because those documents don’t’ have photographs or fingerprints. That’s where Border Patrol agents’ experience comes in.

Even when the adult is sent by the cartels across the Rio Grande, the desert or the border wall mixed in with group of children, the agents either on the field or at the processing center ask questions and compare the answers to the documents.

But what happens when the fake minor doesn’t carry any documents and says he’s 16?

“If the agent on the field thinks something’s going on he will raise a red flag for the (folks) at the processing center,” said U.S. Border Patrol agent Joel A. Freeland.

That’s where a team of agents from the El Paso Sector Intelligence Unit, the El Paso Sector Foreign Operations Branch and Homeland Security Investigations leverage resources to prevent the cartels from sneaking a customer into a room full of children.