FBI: No signs ricin letters connected to Boston attack

WASHINGTON – Investigators say there are no signs of a link between the Boston Marathon bombings and potentially poisonous letters sent to the President Obama and a U.S. senator.

An FBI statement issued Wednesday said the investigation into the letters continues and more may be received. One letter was addressed to Sen. Roger Wicker (R-Miss.), the other to the president. Both were detected Tuesday at off-site mail-screening centers and did not reach the White House or the Capitol.

The letter addressed to Obama contained a “granular substance that preliminarily tested positive for ricin,” a toxin that can be deadly even in small amounts, the FBI statement said.

FULL COVERAGE: Boston Marathon attack

A third screening center also reported a positive ricin test Wednesday morning and mail at the center was being tested further, the FBI statement said.

Suspicious mail is routinely discovered at the screening centers, officials noted. But the presence of the potentially fatal poison the day after the Boston bombings had raised questions about links between the incidents.

The FBI on Wednesday sought to tamp down such speculation.

“There is no indication of a connection to the attack in Boston,” the statement said.

The incident carried echoes of the aftermath of the Sept. 11, 2001, attacks, when a series of anthrax mailings to U.S. senators kept an already rattled capital on edge for weeks. Ricin also was found in a Senate mailroom in 2004.

Law enforcement and White House officials noted that the mail discovered this week did not reach its intended destination and the system developed for screening all envelopes and packages bound for White House and the Capitol appears to have worked properly.

PHOTOS: Explosions at Boston Marathon

When a suspicious powder is found, it is tested on site before being sent to a laboratory for a more thorough analysis. Those tests can take up to 48 hours to complete and sometimes contradict the preliminary test. The letters discovered Tuesday are currently at the lab, the FBI said.

White House spokesman Jay Carney said the president had been briefed on the incidents, but he had no comment on Obama’s reaction.

Follow Politics Now on Twitter and Facebook

Kathleen.hennessey@latimes.com

Twitter: @khennessey