A lab test reveals nothing hazardous in a white powder that briefly forced the evacuation of the FBI's regional headquarters in Salt Lake City.

The FBI is still trying to identify the powder. It spilled out of an envelope Friday when an employee opened it inside a special container used to screen bureau mail.

The scare forced the FBI to evacuate a 13-story office building while a hazardous-materials crew retrieved the letter. A dozen other tenants share the building.

FBI spokesman Juan Becerra says he can't elaborate on the nature of the "hate mail" that accompanied the powder. The case remains under investigation.

The powder was initially tested for anthrax, which can be fatal.