WASHINGTON — A 43-year-old man was arrested Monday outside Seattle and charged with sending 11 packages containing explosive black powder to federal addresses in the Washington, D.C., area, including the White House and several military installations.

Investigators said they do not have a clear motive in the case. They said each package contained a glass vial or small bottle filled with powder, a fuse and a global positioning device. The packages also had typewritten letters that the FBI described in a criminal complaint as containing “ramblings about neuropsychology, mind control and other subjects including terrorism.”

Authorities identified the suspect as Thanh Cong Phan, who lives in Everett, Washington. He was arrested at his trailer by Snohomish County sheriff’s deputies and federally charged with interstate shipping of explosive materials.

Many of the packages were intercepted at screening facilities on the receiving end. None exploded, and no one was harmed. But federal authorities said buildings were evacuated and law enforcement scrambled at each location, such as on Monday at the National Defense University on the grounds of Fort McNair in Southwest Washington.

Authorities said packages allegedly sent by Phan also were addressed to the FBI headquarters, Fort Belvoir, Joint Base Anacostia-Bolling, the CIA in Langley and the Naval Surface Warfare Center in Dahlgren, Virginia.

Phan appeared briefly Tuesday in federal court in Seattle.

His relatives could not be reached for comment after the appearance, and his federal public defender, Ashwin Cattamanchi, declined to comment.

Phan was ordered detained until a hearing Friday.

The FBI alleged in the criminal complaint filed Tuesday that Phan has sent hundreds of letters over the past three years to government agencies “containing similar incoherent ramblings” as were in the letters accompanying the most recent packages.

Officials cautioned Tuesday that additional packages may have been sent to mail-processing facilities in the District area and said they remain on alert.

The FBI said it is working with local law enforcement agencies and reminded the public to “remain vigilant and not touch, move or handle any suspicious or unknown packages.”

The U.S. Attorney’s Office for the Western District of Washington said a U.S. Postal Service inspector traced one of the packages from an FBI mailing facility in Baltimore where it had been received back to a post office in Mill Creek, Washington. Surveillance photos at the post office’s self-service kiosk appeared to show Phan mailing the package, the statement says.

The package was addressed to “FBI Head Quarter” and had a return address of “NAVAL Cpt Mark, 200 W. Marine View, Everett Wa.”

The criminal complaint says investigators found a letter, a fuse, a GPS device and a half-ounce vial containing black powder that tested positive for the flammable compound nitrocellulose in the package that arrived in Baltimore. The vial had a screw-on metal capwith a hole in it; the fuse went through the hole and into the powder, the court filings show.

Authorities said that the vial or jar “would provide sufficient confinement to make the powder detonable” and could have caused “significant injury to a person who was in proximity to the object” if it had been detonated. It was unclear whether the device could have been activated remotely.

U.S. Postal Inspector Justin Lothyan used the package’s tracking number to determine it had been sent from Mill Creek, the criminal complaint said.

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