LAS VEGAS, Nevada (CNN) -- Officers who found the deadly poison ricin in a Las Vegas, Nevada, extended-stay hotel room also discovered firearms and an "anarchist-type textbook" with an entry about ricin bookmarked, police said Friday.

The deadly poison ricin and an "anarchist-type textbook" were found in a room in this Las Vegas hotel.

Two tests had confirmed the substance found was ricin, and that a man who was staying there has been hospitalized for more than two weeks and is in critical condition, police said Friday.

The 57-year-old man, whose name was not released, summoned authorities February 14 and asked to be transported to a hospital because of difficulty breathing, Kathy Suey, deputy chief of the Las Vegas Metropolitan Police Department, told reporters.

But police were not aware of the ricin's existence until Thursday, when a second man, who identified himself as a relative of the victim, went to the Extended Stay America room to clear the victim's possessions out and found the substance. That man brought the poison, which was in vials in a plastic bag, to the manager's office, and police were notified.

"He felt it was something that required police attention," said Las Vegas police Capt. Joe Lombardo. "He brought it to the management and said that 'I'm not comfortable with whatever this item is.'" Watch how ricin can be used to kill »

Lombardo said police first were called to the room on Tuesday after weapons were discovered there. He said officers discovered "general firearms," which have been impounded, and an "anarchist-type textbook" marked at an entry on ricin.

The room was tested for ricin at that time but none was found, Lombardo said. When officers returned Thursday, they found the ricin, but a test of the room showed it was not contaminated.

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

Although seven people were checked as a precaution Thursday, all have been released, Suey said, and none is showing signs of ricin exposure.

Suey said police do not know if the man staying in the room manufactured the ricin, as he has been unable to speak to investigators.

"We don't know an awful lot" about the victim, Suey said. "For the last 12 hours, our efforts have been on the containment and cleanup of the area and areas where there could have been exposure. ... We are now going forward with an investigation."

A report from the Washington Regional Threat and Analysis Center said the FBI considers the discovery "criminal in nature with no nexus to terrorism." The report was sent to law enforcement agencies and was obtained by CNN.

Two Las Vegas labs confirmed the substance is ricin, Suey said. However, the hotel room and other areas tested negative for the poison, police said in a statement issued by the Threat and Analysis Center.

Lombardo said a room at The Excalibur hotel was tested "as a precautionary measure" and found to be safe.

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"At this point we feel extremely positive we have all the ricin involved and there is no terrorist threat," Lombardo said.

Pets were also in the hotel room, Suey said. Two of the animals were fine; the third, an ailing dog, was euthanized after having been without food and water in the room for a week, she said.

Ricin is a toxin extracted from castor beans. Several of the beans were also found in the room, Suey told reporters.

As little as 500 micrograms of ricin -- an amount the size of the head of a pin -- can kill an adult in three to five days, according to the federal Centers for Disease Control and Prevention. The poison can come in the form of a mist or a pellet and can be dissolved in water or weak acid, according to the CDC.

It has limited medical uses -- it can be used to kill cancer cells and destroy bone marrow cells.

The discovery of ricin typically alarms law enforcement agencies because authorities in several countries have investigated links between suspected extremists and ricin. But Lombardo agreed with the assessment that the discovery is not considered a terror incident "at this point."

He said ricin is not illegal to own, but is illegal if processed to be used for poisoning.

"This is a continuing investigation," he told reporters Friday. "We don't know if the guy manufactured the ricin or not. That's our concern."

CNN's chief medical correspondent, Dr. Sanjay Gupta, said although a small amount can kill somebody if injected, tons of the substance would be needed to make it a mass terrorism tool.

He said there are three ways someone might be exposed to ricin: inhalation, ingestion and injection. If it is inhaled, a person 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, Gupta said. E-mail to a friend

CNN's Kevin Bohn contributed to this report.

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