CHICAGO (CBS) — The Dirksen Federal Courthouse was closed for 2 1/2 hours Monday morning, due to a hazardous material scare, but no dangerous substances were found.

Around 7:45 a.m., an air quality alarm went off in the Dirksen building at 219 S. Dearborn St., prompting a hazardous materials response by the Chicago Fire Department.

Everyone already inside was ordered to shelter in place, and the building was closed.

Firefighters conducted air quality tests in the building, and the adjacent Blue Line subway station. All air quality tests came back as normal, and the building was reopened at about 10:15 a.m., according to the U.S. Marshal’s office.

No injuries were reported.