ATLANTA — An envelope containing an unknown black powder-like substance prompted a hazmat investigation at a federal office building on West Peachtree Street.

Atlanta Fire Rescue crews responded after the envelope was discovered inside the ICE office on the 25th floor, leading officials to isolate the area and begin testing. Law enforcement maintained a large presence at the building during the response.

The affected area was immediately isolated, and specialized hazardous materials personnel began an assessment. Hazmat crews screened the envelope and substance for chemical and toxic substances, radiation, narcotics and explosives. Radiation monitoring and atmospheric readings were also conducted.

All tests came back negative, and no hazardous materials were detected.

One person was treated at the scene as a precaution. Authorities said there were no injuries.

Atlanta Fire Rescue says the evacuation of a floor in a federal office building and the testing of an unknown substance during a busy weekend shows they are ready for major events like the World Cup.

WSB Radio’s Michelle Wright contributed to this story.