RIVERTON — Authorities are searching a home here and a series of storage sheds connected to vials of deadly ricin that were found in a Las Vegas motel room.

Dressed in hazmat suits and flanked by a massive emergency response, FBI agents served search warrants today in connection with the ricin investigation. Authorities were expected to be on the scene most of the day.

"The search warrant and affidavit have been sealed," FBI Special Agent in Charge Tim Fuhrman told reporters Sunday. "This investigation involves possible contamination of a highly toxic substance, ricin."

Homes surrounding Thomas Tholen's place near 13400 South and 3000 West have been evacuated while authorities search the rambler-style home on this normally quiet suburban street.

"There's no danger. They're just taking precautions," neighbor Tammy Ewell said as she drove off in her mini-van.

Late this afternoon, Salt Lake County Sheriff's deputies allowed everyone to return home. Tholen's home continues to be searched. Authorities would not say if they found anything of consequence, but said there is no public health danger.

A large portion of 13400 South is closed while the searches are being conducted.

"Is there ricin in there?" a woman asked a Salt Lake County Sheriff's deputy manning the barricade.

"They don't know yet," he replied.

At 9528 Bagley Park Road in West Jordan, agents were searching several storage sheds that had been rented by Roger Von Bergendorff, who has been hospitalized since Feb. 14 in Las Vegas with symptoms similar to ricin poisoning.

Von Bergendorff, 57, lived with his cousin, Tholen, until recently. He moved to Las Vegas and was staying at an extended-stay motel when he fell ill. Tholen, 53, found the vials of ricin in the room and took them to the motel office. Six people had to be decontaminated when it was learned it was ricin. On Saturday, Tholen's wife and daughter were decontaminated when they arrived home from Las Vegas, authorities said.

None tested positive for ricin exposure, the FBI said.

Fuhrman said Tholen is back in Utah and is cooperating with the FBI. Von Bergendorff is unconscious and unable to communicate with Las Vegas police.

"Clearly we are trying to determine the circumstances with respect to Mr. Von Bergendorff's association with ricin," Fuhrman said.

Authorities are trying to figure out how the vials came to be in Von Bergendorff's motel room. The FBI refused to say if either man is considered a suspect or a "person of interest" in their investigation.