WASHINGTON - The FBI said on Thursday that more tests may be necessary to determine the potency of a granular material identified as ricin that was packed into letters sent to President Obama, a US senator and a Mississippi judge.
Last week, the FBI said laboratory testing had confirmed the presence of the toxin in the letters. But FBI spokesman Chris Allen said Thursday he was reluctant to say all tests were complete because "they may be doing more tests on it as the investigation is ongoing."
The Centers for Disease Control said Thursday it had finished its evaluation of the material and sent the results to the FBI and other agencies. She said the CDC could not discuss its analysis because the investigation is continuing.
In Mississippi, the FBI continued its pursuit of the case after last week releasing its original suspect, a man who was arrested after preliminary field tests of the letters detected the chemical agent.
"I can confirm that the CDC did receive samples of material for testing. We have completed the tests and reported the results to partners, including the FBI," CDC spokeswoman Barbara Reynolds said.
Ricin, which is made from castor beans, is a poison that can be deadly to humans and is considered a potential terror weapon, particularly if refined into an aerosol form.