Jennifer Sizemore, a spokeswoman for SNHD, confirmed Tuesday that the CDC sample came back positive.
Police found vials of ricin, firearms and an anarchist-type textbook tabbed to a section on ricin and castor seeds in Bergendorff's Las Vegas motel room on Feb. 22. He remains hospitalized in Las Vegas, but authorities have not yet linked his illness to exposure to ricin, Sizemore said.
"We still don't know about the condition of the individual," said CDC spokesman Von Roebuck. "He's still under evaluation."
On day four of their inquiry, Salt Lake City FBI agents were still investigating who Bergendorff is and what connection, if any, his cousin's home in Riverton played in the discovery of the ricin.
To this point, the investigation remains a public safety issue, not a criminal investigation, Salt Lake City FBI special agent Juan Becerra said Tuesday. Charges have not been filed and no indictments have been issued.
"We're [still] investigating how the problem became," he said.
Salt Lake City agents on Sunday wrapped up their investigation at a home in Riverton owned by Bergendorff's cousin, Tom Tholen, and at several storage units Bergendorff rented in West Valley City. The FBI is not revealing what was taken from the home and the storage units.