Tests Show Letter Sent To Obama Contains Poison Ricin

uthorities said Wednesday they had intercepted a letter to the White House that tested positive for ricin poison.

The Secret Service acknowledged the letter addressed to President Obama contained a suspicious substance, and the FBI later said tests showed it was ricin, the same deadly toxin sent in a letter addressed to Sen. Roger Wicker. The Wicker letter was made public on Tuesday.

News that the letter to Obama was being investigated came as a flurry of other reports of suspicious letters and a package caused the evacuation of parts of two Senate buildings and set nerves in Washington on edge.

The letter contained “a granular substance that preliminarily tested positive for ricin,” an FBI statement said. But the statement added: “There is no indication of a connection to the attack in Boston,” where three people were killed in bombings at the Boston Marathon on Monday.

The Secret Service said the letter to Obama was received at a mail screening facility on Tuesday.

“This facility routinely identifies letters or parcels that require secondary screening or scientific testing before delivery,” the Secret Service said in a statement. “The Secret Service White House mail screening facility is a remote facility, not located near the White House complex, that all White House mail goes through.”

“The Secret Service is working closely with the U.S. Capitol Police and the FBI in this investigation,” Secret Service spokesman Edwin Donovan said in a statement.

Parts of the Russell and Hart Senate office buildings were cleared while officials investigated suspicious letters and a package, a Capitol Police spokesman said.

CNN read a statement from a spokesman to Senator Richard Shelby, saying that Capitol Police were investigating a suspicious package that had been delivered to their office.

Senator Carl Levin said one of his Michigan regional offices had received a suspicious-looking letter, but it was not opened. Authorities are investigating, Levin said in a statement.

On Tuesday U.S. authorities intercepted a letter sent to Mississippi Senator Roger Wicker that preliminary tests showed contained the deadly poison ricin.

Ricin from the castor oil plant Ricinus communis, is a highly toxic, naturally occurring protein. A dose as small as a few grains of table salt can kill an adult human.

White House press secretary Jay Carney said Obama had been briefed twice on the investigation. “He was briefed last night and again this morning,” Carney said.