(NewsNation) — U.S. Border Patrol agents intercepted two suspected drugged children being smuggled across the U.S.-Mexico border, the second such incident in the El Centro Sector in California within days, sources within the agency exclusively confirmed to NewsNation. 

The incident occurred when a U.S. citizen with an extensive criminal history attempted to smuggle two Mexican children, ages 4 and 8, through the San Luis port of entry in Arizona on foot.  

The woman possessed Navajo birth certificates that did not belong to the children, sources said. 

Agents stopped the vehicle carrying the children at a Border Patrol checkpoint on Highway 86 in El Indio around 8:45 p.m. Wednesday. The children appeared drowsy, and a bottle of liquid melatonin was found next to them in the vehicle. 

One child is now acting as a material witness against the driver, while the other was turned over to the Department of Health and Human Services’ Office of Refugee Resettlement. 

The U.S. Attorney’s Office has accepted the case for prosecution. 

Former Homeland Security Investigations Special Agent Victor Avila told NewsNation that “this is an SOP [standard operating procedure] of the child traffickers.” He explained that this method is used to maintain better control over the children. 

This incident follows a similar case in the El Centro sector just days earlier, where agents reported encountering a child who required a sternum rub to become coherent. However, no sleep aids were found in that instance. 

According to federal fact sheets, traffickers often target unaccompanied minors and vulnerable families, knowing that the children have no way to protect themselves. Authorities believe this tactic of sedating children is a way of making sure the children are seen but not heard by border authorities. 

Multiple reports of these druggings have come to light in recent weeks. 

In Arizona, U.S. Customs and Border Protection (CBP) officers at the San Luis port of entry intercepted a woman attempting to smuggle two children across the border on Aug. 29. 

The children, aged 8 and 11, had also been sedated. The woman, an American citizen, presented birth certificates that didn’t belong to the children. The suspect was arrested and the children were turned over to authorities. 

And in Laredo, Texas, a 23-year-old woman has pleaded guilty to smuggling a toddler across the border, sedating her with melatonin gummies and using a fraudulent birth certificate just days ago. That suspect was part of a child smuggling operation that targeted young children under 5 years old. 

Members of the smuggling ring pretended to be related to the children when crossing the border, a common tactic. 

A recent House Subcommittee on National Security, the Border, and Foreign Affairs report said that as many as three in 10 children had no familial relationship whatsoever to the adults that claimed them. 

During the Trump administration, DNA testing was used to verify familial relationships at the border in an effort to crack down on smugglers posing as family members. 

While the DNA testing program ended during the Biden administration, some tests are still being conducted for specific age groups of migrants during their appointments with CBP One. 

NewsNation’s Jorge Ventura contributed to this report.