LAS VEGAS, Nevada (CNN) -- A man who stayed in a Las Vegas hotel room where ricin was found is in critical condition at a hospital, where he has been since mid-February, said a Las Vegas Metropolitan Police Department official.
A man is in critical condition after exposure to ricin at a Las Vegas, Nevada, hotel.
Deputy Chief Kathy Suey said the man called from the hotel asking for medical help on February 14, saying he was suffering from respiratory distress, and was transported to the hospital.
Since he was gone from the extended-stay hotel and not paying his rent, managers began eviction procedures, Suey said at a news conference.
A friend or relative of his who came to remove his belongings from the room found the ricin Thursday, she said. Watch Suey describe how the ricin was found »
Tests confirm the substance found in the room was ricin, police said, but it remains a mystery how it got there. Suey said the man hospitalized was not a suspect and police don't know whether the ricin was his, or if he even knew it was there.
The FBI said it was treating the matter as a criminal investigation and terrorism was not suspected.
Pets were found in the room, Suey said. "Two of those pets are fine. One of the pets is deceased or was put down," she said.
There was no evidence that the animal died from ricin exposure, Suey said. "The dog that was in there was without food and water for a week."
She said the man was unable to speak to police, but a doctor at the briefing said he held out hope the man might recover enough to provide information.
"Usually, if [ricin victims] survive the first three to five days, they usually do fine," said Dr. Lawrence Sands of the Southern Nevada Health District, emphasizing that he didn't know specifics of the case.
As little as 500 micrograms of the toxin -- an amount the size of the head of a pin -- can kill an adult. Watch how ricin poisoning affects people »
Suey said seven people -- including apartment management and police officers -- had been taken to the hospital to be checked out after the ricin was discovered. None showed signs of poisoning, and all had been released, she said.
Symptoms of ricin poisoning can include anything from difficulty breathing, fever, cough, nausea and sweating to severe vomiting and dehydration.
"We did have enough ricin to be of concern," said Capt. Joe Lombardo of the Las Vegas Metropolitan Police Department.
Ricin Poison made from castor beans
Can be inhaled, swallowed or injected
Prevents cells of a person's body making proteins, can cause death
No antidote
Used in cancer treatment and bone marrow transplants
Source: Centers for Disease Control and Prevention
Lombardo said areas of the hotel exposed to the toxin have been decontaminated.
The discovery of ricin alarms law-enforcement agencies because authorities in several countries have investigated links between suspect extremists and ricin.
Ricin is a poison that can be made from waste left over after processing castor beans, according to the Centers for Disease Control and Prevention.
The toxin can come in the form of a mist or pellet and can be dissolved in water or weak acid, according to the CDC. The agency also said the toxin works by getting inside the cells of a person's body and preventing the cells from making the proteins they need.
Lombardo said authorities found castor beans in the room and also powder in a small vial. He said ricin is not illegal to own, but it's illegal if processed to be used for poisoning someone.
Ricin has limited medical uses -- it can be used to kill cancer cells and bone marrow transplants.
CNN's chief medical correspondent, Dr. Sanjay Gupta, said that while a small amount can kill somebody if injected, tons of it would be needed to use as a mass terrorism tool.
Gupta said there are three ways of exposure to ricin: inhalation, ingestion or injections. If inhaled, people may develop fever, a cough, nausea, fluid in the lungs and organ failure.
There is no specific test for exposure and no antidote once exposed, he said.
There have been other reported cases involving ricin in the United States. In January 2005, the FBI arrested an Ocala, Florida, man with no known ties to terrorists or extremists after agents found ricin in the home he lives in with his mother.
Ricin was found in February 2004 in the mailroom of the Dirksen Senate Office Building in Washington. The mailroom handles correspondence addressed to U.S. lawmakers. E-mail to a friend
CNN's Kevin Bohn contributed to this report.
All About Poisoning • Centers for Disease Control and Prevention
The chemical structure of ricin
On February 14, a man staying at the Valley View Extended Stay America hotel in Las Vegas, Nevada was hospitalized after experiencing respiratory distress. The man lapsed into unconsciousness and has been at the hospital ever since.

Since the bills at the hotel were going unpaid, Extended Stay America began to evict the man from the room. Another man, described as either a friend or relative, went to the hotel on Thursday to collect the personal belongings of the hospitalized man.

According to Las Vegas Metropolitan Police Department Deputy Chief Kathy Suey, he found several vials of a white substance. He brought them to the attention of the hotel manager, who called police.

Initial tests, which further tests confirmed on Friday, the substance was the deadly toxin ricin, an extremely dangerous biological agent. Ricin is extracted from castor beans through the waste produced in the manufacture of castor oil. It is currently being used in cancer treatment research. There has been research for its use as a chemical/biological warfare agent. An amount smaller than the point of a pin will kill a human being. It is estimated to be several thousand times more toxic than cyanide and there is no known antidote.

Police cordoned off the area around Valley View between Flamingo Road and Harmon Avenue. Three employees and the man who made the discovery were taken to the hospital as a precaution. So were three police officers. They are all reported to show no signs of poisoning.

Nevada National Guard and other emergency services responded to secure the area. Residents at the Extended Stay America were allowed back into the building late Thursday. The hotel reopened fully on Friday after the room and other areas of the hotel were decontaminated.
Castor beans
The man whose room it was "is in critical condition and he is unable to speak with us right now. We have no indication why the ricin was in that room," said Deputy Chief Suey.

"Usually, if ricin victims survive the first three to five days, they usually do fine," Dr. Lawrence Sands told CNN. However, survivors often have long-term organ damage.

At least three pets were found in the room. "Two of those pets are fine. One of the pets is deceased or was put down," Suey said. "The dog that was in there was without food and water for a week," she added that there was no reason to supect it was exposed to ricin. Castor beans were also found in the room.

Officials have also recovered from the room a firearm, as well as an "anarchist" text containing an article on ricin.

Federal Bureau of Investigation spokesperson Richard Kolko said the incident is being treated as a criminal matter and did not appear to be related to terrorism "based on the information gathered so far."

Captain Joe Lombardo of the Las Vegas Metropolitan Police Department said that ricin is not illegal to own unless it is intended for the poisoning of a person, adding that "We did have enough ricin to be of concern."

In 2003, a man committed suicide in Las Vegas using ricin. There have also been a few incidents where ricin powder was found in the mail. Also in 2003, the United Kingdom had the Wood Green ricin plot which in the end found no ricin.

In 1978, Bulgarian defector Georgi Markov was famously assassinated in London with ricin injected with the tip of an umbrella.