The Defence Department says they are tracking the delivery of suspicious packages to multiple military installations in the Washington, D.C., region.
Army Lt. Col. Michelle L. Baldanza says the incident is under investigation and the Pentagon was referring all inquiries to the FBI.
The FBI's Washington field office said in a statement that the bureau "responded to multiple government facilities" Monday "for the reports of suspicious packages."
According to the accounts, the sites included Joint Base Anacostia-Bolling in the district and at Fort Belvoir, in Virginia.
Army spokesman Michael L. Howard tells the newspaper that a bomb disposal unit from Fort Belvoir confirmed the package tested positive for black powder residue.
No injuries were reported, and the bureau said each package was collected for further analysis.