Suspicious packages have been sent to at least four military bases in the Washington DC region, according to US media reports.
The FBI, Secret Service, Hazmat and an Explosive Ordnance Disposal unit were all deployed to the National Defense University at Fort McNair around 8.30am on Monday local time, where a package tested positive for black powder and residue.
An x-ray of the item revealed a suspected GPS and an expedient fuse were also attached, with all personnel evacuated from the building as a precaution.
Joint Base Anacostia-Bolling also investigated a suspicious package on Monday, as did Fort Belvoir and Naval Support Facility Dahlgren in Virginia.
No injuries were reported at any of the bases and each of the packages were made safe, officials said.