U.S. law enforcement officials say a letter addressed to President Barack Obama preliminarily tested positive for the poison ricin, the second such suspicious envelope to have been detected in the past two days addressed to senior American politicians.
The Federal Bureau of Investigation says the envelope addressed to Obama was immediately quarantined by U.S. Secret Service personnel and a coordinated investigation was initiated with the FBI.
Authorities say they have no reason to believe the suspect letters are related to the bombing attack at the Boston Marathon. They also note false positive tests for ricin are common.
On Tuesday, a separate letter sent to U.S. Senator Roger Wicker was found to have been laced with ricin, a potentially fatal natural toxin, at a remote mail-processing facility.
On Capitol Hill, the Senate Hart Office Building was temporarily closed.
The FBI said additional testing is needed as field and preliminary tests produce inconsistent results. The U.S. Capitol Police said more tests were being conducted.
The letter sent to Senator Wicker tested positive for ricin in three separate initial analyses. The Senate’s sergeant at arms, the chamber’s chief law enforcement and administrative official, said the letter was postmarked in Memphis, Tennessee, located near the Mississippi border.
Ricin previously turned up in a U.S. Senate mailroom in 2004, forcing authorities to temporarily shut down two Senate office buildings. Ricin is highly poisonous — just a tiny drop is lethal for adults.
Tuesday’s discovery evoked memories of the aftermath of the September 11, 2001 terror attacks, when mail laced with anthrax appeared in post offices, newsrooms and U.S. congressional offices. Five people died and several others were made ill.
The FBI attributed the attack to a government scientist who killed himself in 2008.