An envelope sent to Mississippi Republican Sen. Roger Wicker tested positive for the deadly poison ricin, according to multiple media reports.
The envelope was intercepted Tuesday afternoon at an off-site Senate mail facility near Washington, CNN reported. It reportedly first tested positive in a routine test, then again in two followup tests. It was then sent to a Maryland lab for further testing.
But Tom Fuentes, former FBI assistant director and a CNN contributor, said on CNN he had heard from someone close to the investigation that the envelope only tested positive the first time, that the second test was negative, and that the third was inconclusive. It was sent to the lab for a more definitive result.
Homeland Security Secretary Janet Napolitano and FBI Director Robert Mueller told senators about the envelope during a briefing about another matter, Politico reported. Sen. Claire McCaskill (D-Mo.) said it came from someone who frequently writes to lawmakers, and that a suspect had been identified.
Ricin is a highly toxic substance derived from castor beans and can come in the form of a powder, mist or pellet, according to the Centers for Disease Control. There is no antidote, and exposure to it can cause death within 36 to 72 hours.
This post has been updated.