Five people died in the United States when their vehicle careened out of control in Texas some 145 kilometres north of the Mexican border.
Officials say the would-be immigrants were being chased by U-S Border Patrol agents.
The Trump administration announced a controversial so-called "zero-tolerance" policy in early April.
All cases of illegal entry into the country are now referred for criminal prosecution, which can lead to the separation of children from their families.
Nearly 2,000 children were reportedly separated from their families over a six-week period in April and May.
