by Pete Williams and Daniel Arkin

WASHINGTON — At least one man has been arrested in connection with more than a dozen suspicious packages sent to government addresses on the Eastern Seaboard, most of them in the nation's capital, the FBI said Tuesday.

Tranh Cong Phan, 43, was arrested at his home in the Seattle area on Monday. He is scheduled to make his initial court appearance on Tuesday afternoon.

He is believed to have sent a total of 12 packages to military and government addresses in the Washington metro area, officials said.

Officials have said packages turned up at the CIA's mail-sorting facility, a White House mail-sorting facility in suburban Washington, a Navy facility in Dahlgren, Virginia, and two facilities at Fort Belvoir, Virginia — the National Geospatial-Intelligence Agency and another defense university.

FBI investigators found that the packages contained potential destructive devices and appeared to have been sent by the same individual. Some of the packages included letters that one official described as disturbed and rambling.

The deliveries appeared to have been intended to cause fear rather than injure people or cause damage, one official said. But authorities have not confirmed a motive.

Defense Secretary Jim Mattis told reporters on Tuesday that all of the packages mailed to Defense Department facilities were under the control of federal authorities.

"Basically there's a set procedure, they went through the procedure," Mattis said.

"We've had nobody injured and all those packages and all the evidence is accessible and is the hands of the FBI right now."