An Aurora man became severely ill after eating take-out from a Colorado Taco Bell, and authorities are investigating whether the meal may have been laced with rat poison.

The incident unfolded on Sunday after the man was argumentative with staff at the fast food spot at 16776 East Smoky Hill Road, according to the Arapahoe County Sheriff’s Office.

Deputies responded at about 1 p.m. to a disturbance and determined that a customer was upset because the soda machine was broken down and he couldn’t get a soda with his food order, said Deputy John Bartmann, a sheriff’s spokesman.

There was a verbal argument, but no crime was committed, Bartmann said, so deputies left.

At 7:50 p.m. the sheriff’s office was contacted by a hospital about a man being treated for illness, possibly connected to rat poisoning in his food. The man at the hospital was the same man who had argued with staff at the Taco Bell.

The man told investigators that he had taken his Taco Bell order home, did some house chores and watched television, eating his takeout at about 7 p.m., Bartmann said.

The man told investigators he immediately didn’t feel well and began vomiting, Bartmann said. The man called 911 and was taken to a hospital.

Sheriff’s deputies went to the hospital, the man’s apartment, and back to the Taco Bell, where staff was cooperative, Bartmann said. Investigators are looking at evidence including a video feed of the production line at the restaurant. Remnants of food at the apartment are being tested.

On Wednesday, Bartmann said that it’s too early in the investigation to definitively say whether the food was poisoned. There was, however, a greenish-grey substance found in the food that appears to be a foreign substance, police said. An investigation is ongoing.