WASHINGTON – A letter addressed to President Obama, containing a suspicious substance, was intercepted at a screening facility outside the White House, the Secret Service said on Wednesday.

The letter was received on Tuesday – similar timing to the letter addressed to Senator Roger Wicker, Republican of Mississippi, which tested positive for ricin. The letter had similar markings and is similar in appearance to the one addressed to Mr. Wicker, according to a law enforcement official.

The Secret Service did not disclose what was in the letter or provide any details, saying it was intercepted in a facility that "routinely identifies letters or parcels that require secondary screening or scientific testing before delivery.”

The mailing facility is not close to the White House grounds, the Secret Service said. An official said the Secret Service is working with the United States Capitol Police and the Federal Bureau of Investigation.

Parts of Senate office buildings have been cleared because of suspicious packages, showing a heightened anxiety on Capitol Hill. But the Capitol Police said they were not aware that a second suspicious letter to a member of Congress had been intercepted. ABC News reported that a second letter had been received.

Agencies