Among those to receive the packages and rambling letters, reported NBC News, were the National Defense University at Fort McNair and Joint Base Anacostia-Bolling, both in D.C, and two mail processing sites, one for the Central Intelligence Agency and another for the White House.
One package caused the evacuation of Fort McNair, where it later "tested positive for explosive residue", Reuters says.
The package sent there had an X-ray done, and it indicated what was suspected to be a type of fuse attached, according to Mike Howard, a spokesman for Joint Base Myer-Henderson Hall.
One of those packages contained a vial of liquid and a circuit board, and was also rendered safe, NBC reports.
The FBI is now in possession of the packages and is trying to determine if they were explosive and who sent them. The FBI has collected all of the packages for further analysis.
Multiple independent sources with direct knowledge confirmed to ABC News that authorities have arrested a suspect in the Seattle area in connection with the suspicious packages sent to government facilities.
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In July 1979, for example, NASA's 85-ton Skylab space station burned up over the Indian Ocean and Western Australia. However, in March 2016 China announced that Tiangong-1 had stopped sending data back to earth.
All packages were being analyzed in the Federal Bureau of Investigation forensics lab at Quantico.
Two other packages were sent to sites at Virginia's Fort Belvoir, southwest of Washington. The packages were each rendered "inert" by the facility's disposal units, although that does not mean that they were explosive.
A Central Intelligence Agency mail processing facility and a White House mail processing facility also intercepted suspicious packages.
Some of the deliveries were also accompanied with some long letters, described as rambling and disturbing, according to officials. That package was mailed from Austin, linking it to the serial bomber.
Defense Department spokeswoman Lt. Col. Michelle Baldanza said they are aware of the situation and it is being investigated.
It is not yet clear if the packages are all linked to one another.