Corrections and clarifications: The Taco Bell that the man visited is located in Centennial, Colorado.
A man in Colorado was hospitalized after eating a Taco Bell meal that allegedly contained rat poison, authorities said.
The investigation is currently ongoing, Arapahoe County Sheriff's Office public information officer Deputy John Bartmann told USA TODAY on Thursday.
Authorities are still working to confirm if the man ingested rat poison – and, if so, whether or not the rat poison was put into his food at the restaurant.
As of now, the case is categorized as a criminal attempt homicide, Bartmann said.
The man, who has not been publicly identified, went to a Taco Bell in Centennial Sunday afternoon, Bartmann explained. Officers responded to a verbal disturbance call at the restaurant's drive-thru at around 1 p.m., after the man argued with employees because the soda machine was not working.
The man asked for a free food replacement instead of the drink. He was given an additional burrito at no cost, restaurant manager Lary Swift told CBS Colorado.
"When we got (to the Taco Bell), there was... no criminal activity whatsoever. Just a customer unhappy, arguing with employees," Bartmann said, noting that the man soon left the restaurant.
But later, the sheriff's office dispatch received a call from an area hospital at around 7:50 p.m. that evening.
The hospital said that they had a male patient who had "possibly ingested rat poison," Bartmann said. Deputies who responded to the scene found that the patient was the same man from the earlier incident at Taco Bell.
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The man told officers that, after doing yard work at his house and watching some TV, he ate his Taco Bell food at around 7 p.m.
He "immediately felt a burning sensation and then started to get sick," Bartmann said, adding that the man then called 911 and was soon transported to a hospital.
Deputies who responded to the hospital found "a greenish-gray substance" that they couldn't identify in some of the food, Bartmann said.
Investigators then responded to the Taco Bell location to get further information from employees. The man also allowed investigators to go to his house to retrieve the rest of the food and any further evidence, Bartmann said.
Local health and environmental health officials were also contacted. The Taco Bell location had to dispose of all of its food before reopening. The restaurant was temporarily shut down but it is now open again, Bartmann said.
"We don't carry poison in the restaurant," Swift told CBS Colorado. "We didn't do anything like that. It didn't even add up."
In a statement sent to USA TODAY on Thursday, Taco Bell Corp. said that, "The safety of customers and team members is a priority. The franchisee who owns and operates this location has informed us that they are working with local authorities in their investigation."
Bartmann said that Taco Bell has given authorities all of its surveillance video, which investigators are still reviewing. Investigators are also holding on to the man's food to possibly test for rat poison, depending on how the case moves forward in the future.
The man has been released from the hospital, Bartmann said. He didn't know his current condition.
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Experts stress that ingesting rat poison is very dangerous for humans. The University of Kansas Health System notes that symptoms of poisoning can include damage to kidneys and other organs, seizures, bloody diarrhea, bleeding gums, hair loss and bruising.
It also may take a few days after exposure for symptoms to develop. "If left untreated, poisoning can lead to death," the National Pesticide Information Centers says.
This article originally appeared on USA TODAY: Taco Bell rat poison claims in Colorado prompt police investigation