The building at 26 Federal Plaza in Lower Manhattan was evacuated on Thursday afternoon following reports of an unknown white powder.
The FDNY said a call came in just before 4 p.m.
Saying the powder was reported found in the mailroom on the ninth floor of the building, which is home to the Department of Homeland Security and the New York City field office of U.S. Immigration and Customs Enforcement, among other agencies.
First responders and hazmat units were on the scene with four minutes, authorities said.
"Today's event was under control almost immediately, without incident," Deputy Mayor for Public Safety Kaz Daughtry said.