Still denying there might be a terrorist connection, authorities are searching the Utah home of a man lying in criticial condition in a hospital who stayed in a hotel room where a quantity of the deadly toxin Ricin was discovered:

F.B.I. agents on Sunday searched a home and storage space in Utah for evidence that might explain why a man believed to have been exposed to ricin had the deadly substance and what he intended to do with it.

The case of the man, Roger Von Bergendorff, 57, who remained critically ill in a local hospital Sunday, has set off a criminal and public-health investigation spanning two states after vials of ricin, along with castor beans from which the dangerous white powder is derived, were found Thursday in his room at an Extended Stay America hotel near the Las Vegas Strip.

While the F.B.I. has said the incident had nothing to do with terrorism, Mr. Von Bergendorff’s room at the long-term hotel also contained several guns and a book on anarchy tabbed to a page explaining how to manufacture ricin, the Las Vegas police said.

Mr. Von Bergendorff has been hospitalized since falling ill from respiratory distress on Feb. 14.

Neighbors in Utah described Mr. Von Bergendorff as a peculiar loner commonly seen in brown slacks and a brown shirt. Pauline and Grant Dansie, who live three doors down from Mr. Tholen, said Mr. Von Bergendorff spent six weeks last summer searching their backyard daily for a missing cat that he eventually said he found.

“He’s just a little bit different,” Mrs. Dansie said. “He was so obsessed with this cat; it was really strange. He didn’t really act like he wanted to be a friend. I remember one time he put a cat trap out in our field, and he caught our neighbor’s cat. We told him he had to give it back.”

Mr. Von Bergendorff, who is believed to be a computer graphic artist whose work has appeared on several science fiction novels, appears to have a lengthy history involving pets and animals. The police also found three cats and an emaciated dog in his hotel room; the local shelter took custody of the animals, but the dog was so starved and parched it had to be euthanized.