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.

His cousin, Thomas Tholen of Riverton, Utah, found the ricin in the hotel room when he entered on Thursday to collect Mr. Von Bergendorff’s belongings because hotel managers had started eviction proceedings.

Mr. Von Bergendorff had lived with Mr. Tholen until last fall, prompting investigators to don hazardous material protection suits and search Mr. Tholen’s home for ricin. Mr. Tholen’s room at the Excalibur Hotel-Casino was also checked Friday for ricin, but the police said none was found.

“The long and the short of it is that the search is continuing but it’s gotten a lot slower due to the methods and efforts involved in conducting this kind of search,” Juan Becerra, a spokesman for the Federal Bureau of Investigation, said of the effort in Riverton, about 20 miles south of Salt Lake City.

“The investigation continues,” Mr. Becerra added, “but our primary focus right now is to determine if there is any kind of danger to the public here.”

Mr. Tholen could not be reached on Sunday, but he told The Associated Press on Saturday that Mr. Von Bergendorff was “holding his own” at Spring Valley Hospital in Las Vegas.

Mayor William Applegarth of Riverton joined local police officers at 7 a.m. Sunday to knock on doors of several of Mr. Tholen’s neighbors and to suggest they evacuate for the day. Three families left and were let back into their homes by sundown.

“This has been a major shock,” Mr. Applegarth said. “I don’t believe there is any danger to the public.”

In Las Vegas, epidemiologists from the Centers for Disease Control and Prevention arrived Sunday from Atlanta to assist local public health officials in determining whether Mr. Von Bergendorff was sickened by ricin, as is suspected.

“They’re going to be looking through the charts to see what they can determine,” said Jennifer Sizemore, spokeswoman for the Southern Nevada Health District. “As I understand it, after a certain period of time the ricin metabolizes, so making a clear determination may depend on what there is in the charts, what there is to look through, what samples may have been taken.”

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.

Public records show that Mr. Von Bergendorff lived for several years in the 1980s and 1990s with a relative, Fred Bergendorff, in La Mesa, Calif. Mr. Bergendorff, who died on Jan. 27, was the founder of the Pet Place, a charity focused on assisting homeless pets, and the host of the organization’s long-running TV and radio programs in Southern California.