The FBI on Wednesday took into custody a former U.S. Navy sailor suspected of mailing envelopes containing potentially toxic material to the Pentagon and the White House.

The suspect has been identified as William Clyde Allen III of Logan, Utah, the Utah U.S. Attorney’s Office confirmed to The Hill.

“Federal prosecutors in Utah authorized a probable cause arrest of Mr. Allen this afternoon. We anticipate filing charges Friday,” office spokeswoman Melodie Rydalch said in a statement.

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Chief Pentagon spokeswoman Dana White said Wednesday that multiple letters mailed to Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE and Chief of Naval Operations John Richardson contained castor seeds, from which the toxin ricin is derived.

White issued the statement after the Pentagon Force Protection Agency on Tuesday detected a substance suspected of being ricin during mail screenings at the building's underground screening facility.

Ricin is easy to produce and is potentially deadly if made into a pure power form that can be inhaled. The toxin has also been used in terror plots.

Suspicious envelopes addressed to President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE were also intercepted on Monday by the U.S. Secret Service.

The Herald Journal reported that Allen was arrested in Logan, roughly 80 miles north of Salt Lake City. An FBI crime lab was on scene, and the public was warned to stay away from the area due to possible hazardous chemicals, FBI Salt Lake City field office spokesman Doug Davis told the outlet.