WASHINGTON — Federal authorities said on Tuesday that they had intercepted multiple packages suspected of containing ricin, a lethal substance, addressed to President Trump and at least two top Pentagon officials.

In a statement on Tuesday night, the Secret Service said a “suspicious envelope” addressed to Mr. Trump was received at a facility outside the White House on Monday.

“All threats directed towards the president, or any Secret Service protectee, are treated seriously and fully investigated,” the statement said.

The Secret Service did not specify that the envelope contained ricin, but said agents were “working jointly with our law enforcement partners to fully investigate this matter.”