Two American women were arrested at a California immigration checkpoint after border patrol agents determined they were attempting to smuggle two children into the United States.

The women were arrested by Border Patrol agents assigned to the El Centro Sector on Tuesday at an immigration checkpoint on Highway 86 near Westmorland, U.S. Customs and Border Protection (CBP) said in a news release on Thursday.

Authorities reported one woman was driving while the other was in the front passenger seat, and two little girls, ages 10 and 12, were asleep in the back. The identities of the adults were not released.

The little girls were ultimately identified as unaccompanied minors from Mexico, CBP said.

Chief Patrol Agent Gregory Bovino, of the El Centro Sector, said this incident is “how the trafficking of children starts.”

“It’s almost unbearable to think about what heinous crimes await children who aren’t with their parents,” Bovino said. “The border environment has been rife with this type of activity over the past several years, however, the focus has now shifted, and heavy sentences await smugglers who hurt kids.”

US Border Patrol agents discovered two Mexican girls, ages 10 and 12, were inside the car with the two American women, whom they did not know. (REUTERS, File)

Both adult women have been charged with alien smuggling and their vehicle was seized as evidence.