Chicago Public Schools prevented federal officers from from going into an elementary school on Chicago’s Southwest Side Friday and talking to students, according to school officials.

Fearing federal agents asking to search a Chicago elementary school Friday morning were from Immigration and Customs Enforcement, school officials denied them entry. But it turned out they were US Secret Service agents pursuing an investigation.

The U.S. Secret Service says their agents came to the school to investigate a threat, not to enforce immigration laws. Their arrival spread fear in a community on high alert.