The Trump administration on Friday toughened the security requirements for sponsors of migrant children, a move that could make it more difficult for minors who cross the border alone to be released from federal custody and united with family members in the United States.

The policy is similar to one imposed during the first Trump administration, which sought to tighten the vetting process for those living with migrant children.

Immigration activists have argued that onerous requirements helped fuel overcrowding in federal shelters and detention facilities along the border. But reports of security lapses in the way the federal government protects migrant children have also drawn widespread criticism and new scrutiny of the system.

In a memo published on Friday, the Office of Refugee Resettlement, which oversees the care of migrant children, said it would now require that all adult members of a household where a child is to live in the United States must be fingerprinted before the minor can be released by a shelter.

The restriction is similar to one imposed in 2018, which also involved sharing the data with immigration authorities and prompted legal challenges. Advocates for immigrants said the rule discouraged immigrant adults in the United States from coming forward to claim the minors out of a fear they could expose themselves to deportation.

Often, sponsors are undocumented themselves, and therefore wary of any increased risk of deportation associated with claiming sponsorship of a child.