Ricin poison laced letters sent to Obama and lawmakers (Third Lead)

Washington, April 17 (IANS) Two days after the Boston bombings, Washington was Wednesday rattled by the discovery of deadly ricin poison-laced letters addressed to President Barack Obama and several lawmakers.

The letter to Obama was intercepted at an off-site White House mail facility and apparently was from the same sender who mailed a "very similar" letter to Republican senator Roger Wicker Tuesday, the Federal Bureau of Investigation (FBI) said Wednesday.

The letter is being tested further as initial tests can be "inconsistent". Results from full laboratory tests are expected in the next 24 to 48 hours, the agency said.

Government laboratories are also testing samples of a suspicious substance found in letters at off-site White House and Senate mailrooms after preliminary test results pointed to the deadly poison ricin.

Ricin is a highly toxic substance derived from castor beans. As little as 500 micrograms -- an amount the size of the head of a pin -- can kill an adult. There is no specific test for exposure and no antidote once exposed.

The FBI said Wednesday it has no indication of a connection between the tainted letters and Monday's bombings at the finish line of the Boston Marathon that killed three people and wounded 183 others, according to latest reports.

Meanwhile, the Democratic chairman of the Senate Armed Services Committee Carl Levin said one of his Michigan home-state offices received a "suspicious-looking" letter and alerted authorities. "We do not know yet if the mail presented a threat," he said.

Mail for members of Congress and the White House has been handled at off-site postal facilities since the 2001 anthrax attacks.

But Capitol Police were checking out reports of suspicious packages or letters in two Senate office buildings and evacuated the first floor of one those buildings Wednesday afternoon, CNN reported.

Police questioned a man in the area who had a backpack containing sealed envelopes, but a federal law enforcement official told CNN that authorities do not believe the man was connected to the letters found Tuesday.

The letter sent to Wicker had a Memphis, Tennessee, postmark and no return address, Senate Sergeant-at-Arms Terrance Gainer wrote in an e-mail to senators and aides.

(Arun Kumar can be contacted at arun.kumar@ians.in)