Damm declined to comment further.
Riddle said the indictment was not a surprise and that Bergendorff would plead not guilty.
Bergendorff, 57, also was charged with possession of unregistered firearms and possession of firearms not identified by serial number. Among the objects seized from Bergendorff's were a .22-caliber Browning semiautomatic handgun with a silencer and a .22-caliber silencer with no serial number, according to the indictment.
The charges against Bergendorff carry a possible penalty of 30 years in federal prison and a $750,000 fine.
The unemployed graphic designer was hospitalized Feb. 14 and spent several weeks in what authorities variously described as a coma and heavy sedation before he was released from a Las Vegas hospital April 16 into the waiting arms of FBI agents.
Vials containing about 4 grams of "crude" powdered ricin were found in Bergendorff's extended-stay motel room several blocks off the Las Vegas Strip about two weeks after he was admitted to the hospital. Authorities say illegal firearms also were found in the room.
Ricin can be lethal in amounts the size of the head of a pin. It has no antidote, and no legal use other than cancer research.
Prosecutors allege Bergendorff first made ricin in the 1990s, and possessed it while living in the San Diego, Reno and Salt Lake City areas before moving to Las Vegas.
He allegedly told the FBI he kept the ricin in case he needed to hurt unspecified enemies. Authorities said they do not believe it had anything to do with terrorism.
At his initial appearance last Wednesday, Bergendorff, appearing weak and using a wheelchair, told Leen he was no criminal and that he believed he was incapable of ever deploying the deadly poison.
"I didn't use that stuff," he hoarsely insisted, "because I couldn't."
Leen deemed Bergendorff a danger to the community and ordered him held without bail. U.S. marshals have refused to release a booking photo, and Riddle declined a request by The Associated Press to interview his client.
Officials have said Bergendorff's ailments were consistent with ricin exposure, but the source of his illness may never be certain because all traces of the substance are eliminated from the body within days. The ricin in his motel room was found well after he got sick.
Riddle has denied his client was sickened by ricin, attributing his poor health to pneumonia and kidney failure resulting from a mental and emotional downturn after his older brother died in January.
Bergendorff's cousin Thomas Tholen, 54, of Riverton, Utah, was charged this month in Salt Lake City with failing to report a crime. His lawyer, Greg Skordas, denies Tholen knew Bergendorff had ricin.
Police and homeland security officials have said they found no ricin contamination in any place Bergendorff stayed.
