RIVERTON, Utah (CNN) -- Four Utah locations searched for ricin are safe, according to an FBI agent involved in the investigation of a man who may have been exposed to the deadly poison.
Law enforcement officials secure a home outside Salt Lake City, Utah, before searching it Sunday.
"The FBI and its public safety and law enforcement partners re-emphasize that the surrounding areas in all four locations searched pose no threat to public safety," said Timothy Fuhrman, special agent in charge of the Utah FBI office.
In the brief statement, Fuhrman said he would not release what the FBI found in the searches, which were initiated Sunday at a home in Riverton, Utah, and three storage areas in nearby West Jordan, Utah.
The Riverton home belongs to Thomas Tholen, whose cousin, Roger Von Bergendorff, was exposed to the poison, authorities said.
Bergendorff was taken to a hospital February 14 after complaining of breathing difficulties, authorities said, and is reportedly in a coma. Bergendorff, an artist, lived in Tholen's basement before moving to Las Vegas, Nevada, neighbors said. He was exposed to the poison in a Las Vegas extended-stay hotel, a law enforcement official said.
The bureau said there was no public health threat to residents of either Nevada or Utah as a result of the investigation.
Tholen has been cooperating with investigators and is "free to come and go," FBI spokesman Juan Becerra said. "We don't anticipate anything changing in that regard." Watch details of the deadly poison investigation »
"Everything he's told us to this point, we've been able to investigate and corroborate," he said. "So at this point, we have no reason to doubt what he's saying, because of the cooperative nature that he's been displaying toward us."
Tholen, his wife and daughter tested negative for ricin, said Fuhrman.
Police were not aware of the role ricin played in Bergendorff's illness until Thursday, when a second man -- who identified himself as a relative of the victim -- went to the Extended Stay America hotel room to pick up his items and found the substance. The identity of that man is unclear. E-mail to a friend