The Trump administration has identified more than 15,000 cases of adults gaining custody of multiple immigrant children who enter the U.S. without a parent, officials said Thursday, signaling a potential push to prosecute prolific child sponsors.

The Justice Department highlighted cases against three Guatemalan nationals that they say underscore the dangers of improper vetting of sponsors in a program that seeks to unite kids with relatives or family friends after they enter the U.S. Officials said they are investigating numerous other so-called super-sponsors - those who gained custody of more than three unrelated children - to determine whether the sponsors took the kids in fraudulently.

"We will not accept half measures when it comes to securing the border, protecting American lives and saving children from exploitation," Acting Attorney General Todd Blanche told reporters.