By Aamer Madhani and Peter Eisler, USA TODAY
The U.S. Secret Service is investigating a letter containing a "suspicious substance" that was addressed to President Obama, the agency confirmed on Wednesday.
FBI spokesman Paul Beeson said the letter to Obama tested for the substance ricin.
The letter was sent to Obama on Tuesday,and was intercepted at the White House mail screening facility, according to Secret Service spokesman Brian Leary.
The White House mail screening facility is a remote facility, not located near the White House complex, Leary said.
The White House declined to comment, deferring to the FBI and Secret Service which is leading the investigation.
The revelation of the suspicious letter to Obama comes less than 24 hours after U.S. Capitol Police confirmed it was investigating a letter addressed to Sen. Roger Wicker, R-Miss., that tested positive for the poison ricin in a preliminary examination.
Another suspicious package was received Wednesday morning at the Washington offices of Sen. Richard Shelby, R-Ala., according to Shelby's spokesman Jonathan Graffeo. He said the package is being investigated by Capitol Police and it was not known if it was similar to the ones addressed to Obama and Wicker.
The letter to Wicker, which was intercepted at an off-site Capitol mail facility, was found to contain a "white granular substance'' and was quarantined before a preliminary test indicated the substance was ricin, the statement said.
"The material is is being forwarded to an accredited laboratory for further analysis," according to the statement authorized by U.S. Capitol Police Chief Kim Dine.
The Capitol Police have evacuated the first floor of the Hart Senate Office Building due to a suspicious package, CNN reports. People on other floors of the building are being told to go into their offices.