The FBI is investigating suspicious packages with apparent explosive components at several U.S. military installations and intelligence facilities in the Washington, D.C., area Monday, a law enforcement official said.

The National Defense University at Fort McNair in D.C. received a suspicious package about 8:30 a.m., and the building was evacuated.

The package tested positive for black powder, which can be used to make explosives, according to Fort McNair. An X-ray showed what appeared to be GPS and a fuse. It was rendered safe and the building was cleared about 1:15 p.m. The components are being investigated.

Suspicious packages were sent to two sites at Fort Belvoir in Virginia Monday afternoon: The National Geospatial-Intelligence Agency and another defense university. One contained liquid in a vial and a circuit board, the law enforcement official said. It also was rendered safe.

Similar suspicious packages were found at Joint Base Anacostia-Bolling in D.C., a CIA mail processing facility, a White House mail processing facility and Dahlgren Naval Air Station in Virginia, NBC News Justice Correspondent Pete Williams reported. Those were all cleared as well.

It's not clear if any of the packages was an actual working explosive device that could have been detonated.

Some included rambling letters and official described as disturbing.

It’s not clear if the packages are linked to each other, but officials said they do not believe they are linked to the recent bombings in Austin, Texas.

The FBI is examining all of the packages.