"At this point in time, we don't have any indications of any connection to any terrorist act or terrorist activity," Fuhrman said. "That is something we continue look at."

On Friday, Las Vegas Metro police revealed that guns, an "anarchist-type" textbook and castor beans — from which ricin is made — were found in the room where the poison was discovered. Authorities believe they have isolated the locations where the ricin may be.

Neighbors described the Tholen family as "good people," and very friendly.

"Good LDS people," Karma Neider said of the Tholens. "Tom would give the shirt off his back to help you."

"Tom was just trying to help out his cousin," said Lisa Pardee.

Von Bergendorff has been described as aloof, never returning a neighborly wave or really speaking with others on this street. Others said he was an avid animal lover, who cared deeply for his German shepherd dog and his cats. His dog was euthanised after being found starving in the motel room on Feb. 22.

Meanwhile, Riverton city leaders were trying to calm fears about a public health threat. Local health departments were helping to conduct field testing.

"It's not contagious," said Jana Coombs with the Utah Department of Health.

Riverton Mayor Bill Applegarth said he did not believe there was a public health threat in the Tholen home or anywhere else.

"It still makes you nervous," said Applegarth. "I've been overwhelmed with the response from the agencies."

The Centers for Disease Control says that as little as 500 micrograms of ricin — an amount that would be about the size of the head of a pin — could be enough to kill an adult if it were inhaled or injected. Ricin can kill within 72 hours of exposure. It has no antidote, but if a victim doesn't die within three to five days, they will typically recover after being treated with medications to minimize the effects of the poison, the CDC said.

The CDC has documented some reports that ricin was used in the Iran-Iraq war in the 1980s, and some of the deadly toxin was found in al-Qaida caves in Afghanistan.

In 1978, Bulgarian journalist Georgi Markov died in London after he was attacked by a man wielding an umbrella that is believed to have been rigged to inject a ricin pellet under his skin.

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E-mail: bwinslow@desnews.com