FBI officials arrested on Friday a Washington state man suspected of producing ricin, but officials have not determined whether he is tied to the discovery of the toxin on Capitol Hill earlier this year.

Law-enforcement officers arrested Robert Alberg, 37, and charged him with one count of possession of a biological agent or toxin. He is scheduled to appear in U.S. District Court in Seattle on Thursday.

In a telephone interview Tuesday, FBI spokeswoman Robbie Burroughs said agents found ricin in Alberg’s Kirkland, Wash., apartment but it is not clear what he intended to do with the substance.

“He did have ricin as well as the precursor chemicals and ingredients to produce [ricin] in his apartment,” Burroughs said.

It is not clear, however, whether Alberg, who is autistic, had plans to use the ricin.

“There’s no indication at this point that he had used it, but that’s certainly something that’s still under investigation,” Burroughs said. Attorney David Bukey, who has been assigned to represent Alberg, did not return a telephone call seeking comment.

FBI investigators became suspicious of Alberg in November, Burroughs confirmed, when an employee at Sheffield Seed Co. in Locke, N.Y., reported the Washington man had ordered 5 pounds of castor seeds, a sizeable amount. Castor beans are the primary ingredient in ricin, a relatively simple substance to produce.

In recent months, federal law-enforcement authorities have reported several ricin-related incidents, including two letters containing the toxin. Both letters — one addressed to the Transportation Department and another to the White House — were intercepted in late 2003 before being delivered.

In early February, ricin was discovered in the personal office of Senate Majority Leader Bill Frist (R-Tenn.), prompting the shutdown of all three Senate office buildings for several days. Investigators are still searching for a source of that ricin, after failing to find a “hot letter” or other item linked to the toxin in Frist’s office.

The FBI spokeswoman said Alberg is not currently believed to be connected to any of the incidents, including the Capitol Hill discovery.

“We don’t have specific information at this time that leads us to believe he was connected to it,” Burroughs said.

Similarly, a spokeswoman for the FBI’s D.C. field office said: “At this time I’ve not been given any information to indicate that this is connected with Senator Frist’s office.”

The FBI’s Seattle field office has jurisdiction over the case; however, if information links Alberg to the D.C.-area incidents, other offices may become involved, Burroughs said.