WASHINGTON — The Wichita, Kan., office of Sen. Pat Roberts received one of the threatening letters Thursday containing a "suspicious powdery substance" that showed up in other congressional offices earlier this week.
Sarah Little, a spokeswoman for the Kansas Republican, confirmed the arrival of the letter. Two Roberts employees work in the office, she said, and the senator was in Topeka at the time. The Senate is in recess this week.
"While none of the mail received and tested thus far has been found to be harmful, it is clear that the person sending these letters is organized and committed, and the potential to do harm remains very real," according to a memo from Senate Sergeant at Arms Terrance Gainer.
Local law enforcement officials, including a hazardous materials team, were investigating the Roberts incident.
The FBI, the Secret Service, the U.S. Capitol Police and the Postal Inspection Service are involved in investigating the letters, which started arriving at the district offices of several members of Congress, as well as some media organizations, on Tuesday.
"We are working with local law enforcement agencies to determine if any of the mailings are related," said Bridget Patton, an FBI spokeswoman in the Kansas City, Mo., office. "Even sending a hoax letter is a serious crime that will be thoroughly investigated."
The lawmakers include Speaker of the House John Boehner, R-Ohio, and Sens. Dan Coats of Indiana, a Republican, and Patty Murray of Washington state, a Democrat.
Gainer said the letters originated in the Pacific Northwest.
"Senate offices need to take this threat very seriously and remain extra vigilant when handling their mail," Gainer said in his memo. "All letters and packages from unknown sources should be treated as suspicious."
The letters triggered an echo of the episodes in 2001, shortly after the Sept. 11 terrorist attacks, when mail that contained deadly anthrax spores arrived at two Senate offices on Capitol Hill, as well as at several media organizations. Five people died and 17 others were infected.
The FBI called it "the worst biological attacks in U.S. history." The attacks triggered a lengthy and controversial criminal investigation and an overhaul of Capitol Hill mail procedures.
Law enforcement organizations said media organizations should be on the lookout for suspicious letters.
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