March 27 (UPI) -- A Washington state man was arrested Tuesday in connection with suspicious packages found this week at several military facilities near the nation's capital.
Federal authorities said Thanh Cong Phan was taken into custody in the Seattle area Tuesday morning.
Phan, 43, was scheduled to have his initial appearance in the Western District of Washington later Tuesday, the FBI said.
NPR reported Phan was arrested about 12 hours after the first suspicious package was found in the Washington, D.C., area. A motive remains unclear.
One was found at the National Defense University at Fort McNair on Monday and led to the evacuation of the entire building. It tested positive for black powder, a substance often used to make explosives. A subsequent X-ray revealed a GPS-related item and fuse attached to the package.
Others arrived at two sites at Fort Belvoir in Virginia Monday afternoon -- the National Geospatial-Intelligence Agency and another defense university. Authorities said one contained liquid in a vial and a circuit board.
Suspicious items were also found at Joint Base Anacostia-Bolling, mail processing facilities for the White House and Central Intelligence Agency and Dahlgren Naval Air Station in Virginia.
"The FBI responded to multiple government facilities today for the reports of suspicious packages," the bureau said in a statement. "Each package was collected for further analysis by the FBI."
It wasn't immediately clear if any of the packages contained actual working explosive devices that could have detonated, but some included rambling letters that officials described as disturbing.
The FBI investigation comes a week after a series of explosive package bombs around Austin, Texas, came to an end. Police say suspect Mark Conditt delivered the bombs that killed two people and injured others, beginning March 2.
The FBI said it does not believe the cases are related.