A Utah man charged with a federal crime in a case involving ricin has pleaded not guilty.

Thomas Tholen of Riverton made his first appearance in federal court Tuesday since he was indicted April 3.

Authorities say the 54-year-old Tholen knew that ricin, a dangerous biological agent, was being produced by his cousin but failed to report it. He's charged with misprision of a felony.

The cousin, Roger Bergendorff, is charged in Las Vegas with possessing a biological toxin. He was in a hospital for two months after authorities suspect he was poisoned by ricin.

Federal agents say vials containing about 4 grams of "crude" powdered ricin were found in Bergendorff's Las Vegas motel room.