The U.S. Army recently issued a statement and revealed that the packages that were sent to the installations have already been "rendered safe".
Defense Secretary Jim Mattis told reporters on Tuesday that that all of the packages sent to Defense Department facilities are under the control of the federal authorities.
The FBI seized the packages that were stuffed with explosive components such as black powder, fuses, and circuit boards.
At Fort McNair, a suspicious package was delivered at about 8:30 a.m. eastern time, prompting officials to evacuate the building, according to a base spokesman.
Williams said "It's obvious they were on to this person quite quickly", adding that authorities had some indication of their suspicions Monday evening.
GMC Sierra AT4 debuts lifted tech-savvy off-roading trim That black chrome also adorns the LED foglamp bezels, while the window trim, mirror caps and skid plate are done in black gloss. Bumpers, door handles, and grille shell are body colored, and a pair of vertically mounted front towhooks are painted red.
Among the facilities where the packages were shipped were Fort McNair, in the nation's capital, and Fort Belvoir in northern Virginia, both U.S. Army bases.
All the suspicious-package incidents that had been reported throughout Monday morning and afternoon had ended with no injuries.
It is not clear if the parcels all contained working explosives. Odd mailings also arrived at Joint Base Anacostia-Bolling in Washington, DC, the Central Intelligence Agency mail processing center, the White House mail processing center, and Dahlgren Naval Air Station in Virginia. The FBI has collected all of the packages for further analysis.