WASHINGTON (AP) — The FBI says preliminary tests on a letter sent to President Barack Obama indicate the presence of poisonous ricin.

The letter is undergoing further testing because preliminary field tests can be unreliable, creating false positives.

The letter was intercepted at a facility away from the White House. It comes the day after officials said a letter sent to Sen. Roger Wicker tested positive for poisonous ricin. That letter to Wicker, a Republican, was intercepted at a Senate mail facility just outside Washington.

The FBI says there is no indication of a connection to the bombing at Monday’s Boston Marathon.