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Officials are looking for ricin, a highly lethal substance, but say there is no danger to the public.
Roger Von Bergendorff, who had lived in the house and rents the storage units, is suspected of having come in contact with ricin, found in his Las Vegas motel room last week. He remains in a coma in a Las Vegas hospital.
The Riverton house, at 3004 W. 13400 South, is owned by Von Bergendorff's cousin Tom Tholen. Von Bergendorff lived there for nearly 12 months in 2005 and 2006. His rented storage units are at Jordan Self Storage, 9528 Bagley Park Road, West Jordan.
Salt Lake County sheriff's deputies evacuated homes in a two-block area in Riverton this morning, but officials said at a 4 p.m. news conference at Riverton city offices that residents in the homes have been allowed to return. The Tholen's have not been allowed to return to their home, as the search continues.
Traffic on 13400 West was blocked from 2900 West to about 3100 West shortly after 7 a.m., and deputies and Riverton Mayor Bill Applegarth knocked on doors of homes within 300 yards of Tholen's house, said Tammy Ewell, who lives across the street.
Von Bergendorff also stayed in a camper trailer in the garage of Tholen's neighbor, John Walster, for three months after he left Tholen's house in June of 2006. Walster lives across the street and three houses down from Tholen. It is not known whether Walster's house will be searched.
"We're not sure whether to be worried or not," John Walster said Saturday evening. "I'm just worried something may be stirred up if I go cleaning back there."
Walster took in Von Bergendorff, a 57-year-old graphic designer, after he overstayed his welcome at Tholen's house. The men had met at the local LDS ward, where Von Bergendorff had talked about overcoming a drug addiction, Walster said.
When he wasn't delivering pizza part-time, Von Bergendorff mostly spent time with just his two cats and his German shepherd, Walster said. He was polite -- calling the Walsters "Brother Walster" and "Sister Walster" -- and declined invitations to Sunday dinners at the house.
Walster described Von Bergendorff as down-on-his-luck but nice, a loner who could be inexplicably "vindictive" at times. Von Bergendorff mentioned owning a handgun before, Walster said, but never acted violently.
"I never felt comfortable around him," Carol Walster said. "There was just something about him."
In August 2006, Walster said, he asked Von Bergendorff to leave. He eventually packed up Von Bergendorff's things and put them outside. Von Bergendorff told the couple he was leaving for a graphic design job in Las Vegas.
On Feb. 14, Von Bergendorff checked into a hospital complaining of respiratory problems. Tom Tholen came to visit, and contacted motel management Feb. 22 to inform them about pets in the room. The manager contacted police when he found firearms in the room, and police also found an "anarchist-type textbook" tabbed to a section on ricin and castor beans, from which ricin is made, authorities said.
Tholen later found vials apparently containing ricin and gave it to the motel manager. After the vials were taken to the motel office, Tholen and six other people, including the motel manager, two motel employees and three police officers, were decontaminated at the scene and taken to hospitals for examination. None have shown any signs of being affected by ricin, officials said.
As little as 500 micrograms of ricin, about the size of the head of a pin, can kill a human, according to the Centers for Disease Control and Prevention. The only legal use for ricin is cancer research.
Tholen's wife and daughter also went to Las Vegas, according to neighbors. When they returned from Las Vegas without Tom Tholen Saturday morning, FBI agents and sheriff's deputies swarmed the car, neighbors said. They were told to remain in their car for several hours, neighbors said, and were eventually taken into a HazMat tent.
Tim Rogers, who lives behind the Tholens, said he approached two men parked near his house in an unmarked SUV Saturday night, but they refused to identify themselves. "They've been tight-lipped all day," Tonya Rogers said. "Which is a little worrying when you see HazMat trucks outside your house."
Brad Ewell said he was sure the Tholens had nothing to do with whatever Von Bergendorff was up to. He never had a good feeling about him, he said.
"They always say, you never know your neighbors," Ewell said.
The Associated Press contributed to this article.