As investigators seek the source of the ricin that was found in a Senate mailroom, legislative staffers who may have been exposed are being asked to help advance medical knowledge.
A spokesman for Senator Bill Frist, whose office is where the toxin was detected, says nine workers have been asked to give blood samples to Navy researchers. The group was told the samples were to
determine if they had developed antibodies to ricin. That might help researchers looking for an antidote.
Meanwhile, the FBI is expanding its search for the source of the ricin. Since testing has been negative throughout the mailroom, investigators now must consider if the ricin was placed on the machine by someone or if it had spilled out of an older letter and been there for a long time.
Two of the three Senate office buildings closed by the discovery have reopened and the third is expected to reopen soon.