Detectives may be looking at the discovery of a poison-infested vial at a Las Vegas motel as a murder plot that has left one man gravely ill, FOX News has learned.

The toxin known as ricin turned up at the Extended Stay America Motel, leaving one person in critical condition and in the hospital, with some reports suggesting that he may be in a coma. No one else has exhibited signs of ricin poisoning to date, police said Friday.

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Law enforcement officials told FOX that the Las Vegas Police Department is leading the probe and the investigation appears to be focusing on a possible murder plot of some kind. Las Vegas authorities wouldn't confirm that during a Friday afternoon news conference.

"We don't have a lot of specific information," said Kathy Suey, deputy chief of the Las Vegas police Homeland Security division.

One of those exposed to the ricin is in critical condition and might be comatose, according to some accounts, after the vial of ricin was found in his room.

Police on Friday would not confirm an Associated Press report that the man — whose identity wasn't released — was in a coma, but did say he was very sick.

"Right now, we don't know (whether he's conscious)," Suey told reporters. "We know he is in critical condition and he's unable to speak with us right now."

Click here to read Adam Housley's blog on the case.

Suey said the man, whom she described in his 40s or 50s, lived in the hotel room where the ricin was found and went to the hospital Feb. 14 complaining of respiratory distress. He has been there ever since.

She said it wasn't clear whether the ricin belonged to him or whether it was there without his knowledge.

"We don't know whether he was in possession of the ricin," Suey said. "That's part of the investigation. ... We don't know an awful lot right now."

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She added that detectives were looking at whether the man might have been carrying the ricin and targeting someone, or whether he was a victim. No one else has fallen ill.

"So far, we don't have anyone else exhibiting any signs of being affected by this ricin," she said.

Federal and local officials also said there doesn't appear to be a terrorism connection in the case, but identifying the sender and receiver of the package has taken top priority.

"This is not a terror incident at this point," said police Capt. Joseph Lombardo earlier Friday.

A hospital spokeswoman said that there was no danger of the man spreading anything to other patients.

"The patient who has been exposed is not contagious to anyone else, as ricin has to be injected, ingested or inhaled. We are following the universal blood-borne pathogen protocols and cooperating with investigators at this time," said Spring Valley Hospital spokeswoman Naomi Jones.

Jones said the hospital was not shut down and people there were not at risk of exposure.

Authorities were called to the Vegas motel on Thursday and retrieved a package from the motel manager that was determined to be a chemical or controlled substance, Officer Ramone Denby said.

The investigation of the apparent ricin didn't begin until Thursday, after another man brought a vial found in his room to the motel manager and police were ultimately called to the Extended Stay America Motel several blocks west of the Las Vegas Strip.

Two preliminary tests indicate it contained ricin, Denby said. Results from further tests by the Centers for Disease Control and Prevention and a second local lab are expected Friday, according to investigators.

"Ricin has no medical uses other than cancer research," Lombardo said at a news conference Thursday night. "An individual citizen other than being involved in cancer research or cancer prevention would not have any legal means or proper means of having that."

An expert in ricin told FOX News that the field tests done at the hotel were considered primitive, and the forthcoming CDC results would be the most reliable. Those could be completed within as little as 24 hours.

Police cordoned off the area and isolated the room where the substance was found. The motel rents out rooms to occupants, according to Suey, and detectives' first concern was decontaminating the area and making sure everyone was safe and the situation was under control.

Seven other people including the motel manager and some police officers were taken to hospitals for examination but none have shown any signs of being affected by ricin, Suey said.

The motel room had been unoccupied for the past week. Someone who knew the sick man found the ricin in the room and brought it to the apartment manager, according to Suey.

"He claimed to be a relative. We haven't confirmed that yet whether he is a relative or a friend," she said.

The manager had begun an eviction because the sick man hadn't paid his bill, and the friend or relative had gone to retrieve his items, she said.

Police said they had spent 12 hours on containing and cleaning up the site.

"My understanding is cleanup has been done. There should not be a threat to anybody at this time," said Dr. Lawrence Sands, chief health officer of the Southern Nevada Health District.

Suey said there were several pets in the room when officers arrived. A dog was found dead but the animal had gone at least a week without food or water, according to Suey, and she did not attribute the death to ricin.

Three motel employees and another person were quarantined and decontaminated at the site, then taken to hospitals for further testing, Denby said Thursday. All appeared to be in good condition, he said. Three police officers who had been exposed were also taken to hospitals.

It takes between six and eight hours for someone exposed to ricin to show signs of contamination.

Homeland Security officials joined local police in the investigation. Officials from the FBI, Las Vegas Health District, a hazardous materials team and the National Guard also were at the scene.

Ricin is made from the waste left over from processing castor beans and can be extremely lethal. As little as 500 micrograms, or about the size of the head of a pin, can kill a human, according to the CDC.

FOX News' Ian McCaleb, Catherine Herridge, Catherine Donaldson-Evans and The Associated Press contributed to this report.