Outside Terminal B — not long after a group of seven boys was spotted getting off American Airlines Flight 2716, wearing dark hoodies and carrying government-labeled belongings — a circle of about 200 protesters gathered along the taxi line to plan for how they might lend support to other children getting off planes, though there was no way to determine immediately which might have been separated from their parents.

An American Airlines spokesman, Ross Feinstein, said in an interview that it had delayed the flight from Dallas-Fort Worth by 33 minutes until it got reassurances from government officials that these teenagers were not among those who had been separated from their parents. But a cluster of flight attendants who had been on board stood nearby after the children deplaned, visibly distraught. “They lied to us,” one flight attendant said.

Brian Marriott, a spokesman for the Administration for Children and Families, a division of the United States Department of Health and Human Services, said the agency was looking into the matter at La Guardia.