A Tempe city building was evacuated Tuesday morning after an unknown substance was found in a letter, Tempe Fire and Medical officials say.

Emergency crews were called to a building near Mill Avenue and 5th Street, north of University Drive, before 9 a.m. Tuesday.

Fire officials say someone in a city court facility opened a letter and discovered a white powder. Several people were exposed to the unknown substance, including four people who reported minor symptoms, like headaches, believed to be from the powder. One person was taken to a hospital as a precaution.

Investigators say after testing the substance it did not compose any hazardous material and posed no threat to employees or the public.

Multiple police and fire departments from neighboring cities did secondary tests to confirm the building was safe. The evacuation was lifted just after 11 a.m.

Officials say 5th Street, which was closed for the investigation, has since reopened as of Tuesday afternoon.