Robert M. Alberg of Kirkland, Wash., was arrested at his apartment Friday and charged with one count of possession of a biological agent or toxin.
"It is enough to cause concern that it could harm someone, it could kill someone," FBI spokeswoman Roberta Burroughs told CBS affiliate KIRO.
Alberg was held pending a hearing Thursday in U.S. District Court. He is described in court documents as having autism, a developmental disorder featuring a spectrum of symptoms including impairments in communication and repetitive behaviors such as finger tapping or head banging.
Federal criminal justice sources told the Seattle Post-Intelligencer they do not believe Alberg had political motivations for making the ricin and had no plans to use it.
Agents believe Alberg was making the ricin in his apartment on a relative's property but won't say how much was found.
"The ricin was found in his apartment after agents went in there on Friday and once they confirmed it was there, he was arrested and taken into custody," said Burroughs.
The criminal investigation of Alberg began in November when an employee of the Sheffield Seed Co. in Locke, N.Y. warned the FBI in New York that Alberg had ordered 5 pounds of castor seeds, a key ingredient in making ricin. Because the company considered the order unusual, it alerted the FBI. In December, the seeds were mailed to Alberg.
Ricin can be fatal if ingested, inhaled or injected. There is no antidote.
Ricin is relatively easy to make. Unlike anthrax spores, ricin requires little scientific training to engineer and is not nearly as dangerous to handle.
In the nation's capital, ricin was found Feb. 2 on a mail-opening machine in the office suite of Senate Majority Leader Bill Frist, R-Tenn. The discovery led to a shutdown of three Senate office buildings for several days, and about two dozen staffers and Capitol police officers underwent decontamination.
No one was hurt and no suspect or source for the poison has been identified.