Gregory Korte and Kevin Johnson, USA TODAY
Washington-- A letter addressed to Sen. Roger Wicker, R-Miss., tested positive for ricin poison in a preliminary examination, but it is undergoing more definitive analysis before the result is confirmed, according to a statement issued by U.S. Capitol Police late Tuesday.
The envelope, 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 Chief Kim Dine.
Dine's statement also indicated that the FBI was involved in the investigation.
"This is an ongoing investigation; this is a controlled event at an off-site facility. Operations at the Capitol complex have not been affected as a result of the preliminary investigation,'' Dine's statement said.
FBI spokesman Paul Bresson said a field test on the letter produced mixed results, so the letter was referred to a laboratory for a more conclusive examination.
Ricin, a poison from the same bean used in castor oil, must be ingested to be fatal, says Milton Leitenberg, a University of Maryland bioterrorism expert.
Wicker said Tuesday evening there is an "ongoing investigation" and that he wants to thank law enforcement officials for keeping the Capitol complex safe. Senators were briefed on the matter in a closed-door meeting Tuesday night. Coming a day after two blasts killed three people and wounded more than 170 at the Boston Marathon, the ricin-tainted letter spurred renewed fears about terrorism, but there was no apparent connection between the letter and the bombing.
Sen. Claire McCaskill, D-Mo., said authorities have a suspect, but she did not say if an arrest had been made. Terrance Gainer, the Senate sergeant-at-arms, said in an e-mailed message to Senate offices that the envelope had no obvious suspicious outside markings, bore a Memphis postmark and had no return address.
"We were told it's not as deadly as anthrax, but it's still very serious," said Senate Majority Whip Dick Durbin, D-Ill. The letter was intercepted at a suburban Prince George's County, Md., mail facility. "Everything that's sent to us, everything that's mailed to us, is roasted, toasted, sliced and opened," Durbin said.