CHICAGO (CBS) — Three children traveling from Mexico who were detained at O’Hare airport for several hours have been reunited with their mother.

Chicago Mayor Lori Lightfoot tweeted that she appreciated the “responsiveness of [customs agents] following our conversation about the urgency of reuniting the three children with their mother.”

The children, who are U.S. citizens, were returning to Chicago and were detained by Customs and Border Patrol agents along with the man who was authorized to travel with them.

Their parents are undocumented immigrants, and they feared the children were being used so that the parents could be detained by Immigration and Customs Enforcement.

According to WBEZ’s Maria Ines Zamudio, the mother went to O’Hare with Mexican consulate officials.

CBP issued a statement on Thursday evening which said “by law, [the children] could only be released to a parent/legal guardian.”