WASHINGTON--Authorities in Las Vegas said there was no threat of terrorism or widespread contamination after the deadly poison ricin was found in a hotel room, US media reported on Saturday.

A 57-year old man remains hospitalized after staying in the hotel room where the deadly toxin was detected, authorities said.

"I want to assure everybody that the Las Vegas Valley is safe," police Captain Joseph Lombardo was quoted as saying by the Las Vegas Review Journal.

"We don't currently have any terrorist threat at this time or possibility of contamination (due) to ricin."

Police confirmed that guns and an anarchist book with information about ricin were also found in the Extended Stay America hotel and said the circumstances of the poisoning remained unclear.

It was possible the man injured by the ricin was a victim, police told reporters.

The US Centers for Disease Control and Prevention (CDC) meanwhile said it was joining the investigation along with local health agencies, police and the Federal Bureau of Investigation.

The federal agency said on its website it would work "collaboratively" with other public agencies on the case and confirmed "preliminary results of environmental testing at laboratories in Nevada have tested positive for ricin."

The CDC said accidental exposure to ricin was "highly unlikely" and that "it would take a deliberate act to make ricin and use it to poison people."

The man injured by ricin, whose identity has not been released, went to hospital on February 14 complaining of breathing difficulties.

The possible ricin link was not discovered until later, when a person who came to collect his belongings from the room where he had been staying found vials of white powder there on Thursday.

After tests showed the substance found in the hotel was ricin, police sealed off areas that could have been contaminated. The hotel room has not been rented since.

According to the CDC, 500 micrograms of ricin -- about the size of a pin head -- is enough to kill an adult.

The poison is derived from the castor bean plant and can be dissolved in water, injected or sprayed. It attacks the liver and the kidneys.

Castor beans were also found in the room at the hotel, one mile west of the main Las Vegas Strip, police said.

The hospitalized man did not indicate to doctors that he may have been exposed to ricin, so the health district and police were not aware of the possible link.

The hotel was reopened early Friday after public health officials determined they had found and removed all the ricin.