WASHINGTON (Reuters) - A letter addressed to President Barack Obama containing a suspicious substance was received at a White House mail screening facility on Tuesday, the Secret Service said on Wednesday.
The facility is remote and not located near the White House itself, spokesman Edwin Donovan said in a statement.
"This facility routinely identifies letters or parcels that require secondary screening or scientific testing before delivery," Donovan said.
"The Secret Service is working closely with the U.S. Capitol Police and the FBI in this investigation."
On Tuesday U.S. authorities intercepted a letter sent to Mississippi Senator Roger Wicker that preliminary tests showed contained the deadly poison ricin.
(Reporting by Jeff Mason; Editing by Vicki Allen)