U.S. immigration enforcement officers are proposing that fingerprints be taken from all people claiming custody of children who have entered the United States illegally without an adult relative, a measure that opponents said could keep thousands of families apart.

As a new wave of unaccompanied Central American children pours across the U.S.-Mexico border, the proposal underscores the sometimes conflicting goals of federal agencies in dealing with undocumented immigrants, a volatile issue on the presidential campaign trail.

Officials at the U.S. Department of Health and Human Services (HHS), which is ultimately responsible for finding housing for migrant children, told Reuters they have no plans to change fingerprinting policy. They said the proposal — made by U.S. Immigration and Customs Enforcement (ICE) officials in an internal memo seen by Reuters — would delay family reunions and infringe upon the parent-child relationship.