Explosive disposal specialists and hazardous material experts were called into examine a white powdery substance found this morning at the Post office at Marine Corps Base Quantico.
Testing is reported to indicate the substance was negative.
In addition to the FBI National Training Academy being located on the base, It's also home to the FBI's Crime Lab.
According to a posting on the base Facebook page, the closing came as a suspicious letter was found this morning.
Four people, 2 Marine Corps postal specialists, a civilian postal clerk and a patron, were in the building at the time of the discovery.
The Postal facility will reopen later today.