Letter sent to Obama tests positive for ricin, FBI says

The FBI has confirmed that a letter addressed to President Obama has "preliminarily tested positive" for ricin, a day after lawmakers said another letter sent to the Capitol Hill office of Sen. Roger Wicker tested positive for the same substance.

The warnings come amid a flurry of reports on suspicious packages on Capitol Hill. Fox News has learned of several suspicious packages or envelopes in various Capitol Hill office buildings. Capitol Police say three packages that were flagged have been removed and the areas have been cleared. Separately, the office of Sen. Carl Levin, D-Mich., reported a "suspicious-looking letter" at one of the senator's Michigan offices, and other suspicious packages were reported at the Arizona office of Sen. Jeff Flake, R-Ariz.

The package alerts compounded security concerns in the wake of the letter incidents and the Boston bombing, which the FBI has said do not appear to be related.

Both of the initial suspicious letters were apparently intercepted on Tuesday. They never reached the Hill or the White House.

An FBI bulletin obtained by Fox News said the letter sent to Obama is still being screened, though it initially tested positive.

The bulletin said both letters included the phrase: "To see a wrong and not expose it, is to become a silent partner to its continuance."

Both were signed, "I am KC and I approve this message."

The letter to the Mississippi Republican was intercepted at an off-site mail screening facility.

Authorities declined to comment on a suspect or any other aspect of the investigation being led by Capitol Police, but Sen. Claire McCaskill, D-Mo., told the Associated Press police have a suspect in mind.

"The person that is a suspect writes a lot of letters to members," McCaskill said as she emerged from a classified briefing.

Testing is apparently still underway. The letter tested positive for ricin in a field test, but the FBI released a statement Wednesday saying tests have shown "inconsistent results" and the substance is being further analyzed.

According to a Homeland Security Department handbook, ricin is deadliest when inhaled. It is not contagious, but there is no antidote.

Wicker thanked law enforcement officials in a statement for "their hard work and diligence in keeping" those who work in the Capitol safe, adding that the matter is part of an ongoing investigation by Capitol Police and the FBI. "Gayle and I appreciate everyone's thoughts and prayers," he said.