WASHINGTON -- The Trump administration is planning to expand the collection of DNA from migrants who cross U.S. borders, and to include the information in a massive criminal database operated by the FBI.

Two senior Homeland Security officials briefed reporters about the plan Wednesday, but did not say why the DNA data is needed. They also did not say if the DNA sampling would apply to children crossing the border alone and whether it would include asylum seekers.

The officials spoke on condition of anonymity to discuss an ongoing effort.

The effort is separate from rapid DNA testing done on families at the U.S.-Mexico border to help detect adults posing as parents.

It's not known when the new DNA collection would begin. It could face legal challenges from civil liberties advocates.