Children as young as eight are reportedly being drugged and smuggled into the US, sometimes multiple times, by human traffickers posing as parents or other family members, Border Patrol agents are warning.

The New York Post reported that authorities in two such instances have rescued children, including one instance where alleged traffickers had birth certificates for multiple children to which they were not related.

Sources in the Border Patrol told the outlet that there have been increasing cases of smugglers posing as family units and going on to "recycle" the children. One Border Patrol source said, "A few years ago when they were coming in en masse, we had to let family units in. People kept coming in and after a while we noticed the kids were the same, but the parents were different. They were recycling the kids."

"I hate thinking about it because there were thousands of kids and who knows where they all ended up," the source added.

Authorities have said that it is unclear what happens to the children once they are smuggled into the US. The Post reported that many may end up being exploited for child labor and sex trafficking.

Gregory Bovino, the Border Patrol chief of California’s El Centro sector, said, "Sometimes we encounter criminal actions so horrendous they defy human decency."

Bovino said that border agents in one case rescued a child at the California border who was found to have been "heavily dosed with sleep aids to prevent him from talking." The agents discovered that the traffickers had additional birth certificates for other children.

On August 29, officers at the San Luis, Arizona port of entry arrested 28-year-old US citizen and Arizona resident Marlen Contreras-Lopez after she was found with two young children sleeping in her car who had been drugged with sleep aids, federal prosecutors said.

Contreras-Lopez had initially claimed that she was related to the two children and attempted to wake them when officers questioned. When she got out of the car for further inspection, the officers say that one of the children needed to be carried, and the other one "struggled to walk."

"The woman had difficulty waking the children. Officers observed that the children remained extremely groggy. While interviewing the children, officers soon discovered there was no family relationship between the woman and the two minors, ages 11 and 8,” Executive Assistant Office of Field Operations Commissioner Diane J. Sabatino said.

She added that the woman possessed legitimate birth certificates, but they did not belong to the children. The children told officers that they had been given sleep aids "in order to avoid detection."

One of the children told officers that she and the other child, who she said was her brother, were from southern Mexico. They had taken a bus to the Mexican border town of San Luis Rio Colorado, where they were picked up by the woman. She said that their mother was still in Mexico, while they were being sent to live with their mother’s boyfriend.