The operation began at a home and later extended to the school grounds.The agency stressed that it only investigates threats, does not enforce immigration laws.

Chicago Public Schools officials incorrectly said U.S. Immigration and Customs Enforcement Agents attempted to enter a South Side elementary school.

CHICAGO -- The U.S. Secret Service said its agents visited a Chicago elementary school Friday while investigating a threat, hours after school officials mistakenly claimed that U.S. Immigration and Customs Enforcement agents had come to the building.