Pizzeria mishap left at least 85 people intoxicated with THC after infused oil used for dough

At least 85 people accidentally became intoxicated with THC, the psychoactive ingredient in cannabis, after eating pizza, garlic bread and sandwiches from a Wisconsin restaurant, a new report explains.

The unusual incident, which took place in October 2024, was described in a new report published July 24 in Morbidity and Mortality Weekly Report, a regular publication put out by the Centers for Disease Control and Prevention. The report's authors are affiliated with Public Health Madison & Dane County (PHMDC), who warned Wisconsinites of the mass intoxication event as it was unfolding last year.

A statement issued at that time named the restaurant — Famous Yeti's Pizza in Stoughton, Wisconsin — which immediately cooperated with the investigation and was determined to have unintentionally contaminated its food with THC (tetrahydrocannabinol). Live Science contacted Famous Yeti's Pizza for comment on the new report but had not heard back by the time of publication.

The statement urged anyone who had bought food from the restaurant between Oct. 22 and Oct. 24, 2024, to throw away any leftovers and watch for symptoms indicative of THC exposure, such as dizziness, increased blood pressure, increased heart rate, nausea, vomiting, anxiety, panic attacks, paranoia, hallucinations or short-term memory impacts.

"Keep in mind each person's reaction may be different, and the concentration of THC in the pizza can vary by piece," the statement noted. The department later released additional information on social media and its blog to note that leftover grinders (submarine sandwiches), garlic bread and cheese bread from the restaurant were also affected and should be thrown out.

The health department was first alerted to the issue on Oct. 24, when local emergency medical services reported that they'd transported seven people with similar symptoms to the hospital in the prior two days, and all had reported eating food from the same restaurant. The patients' symptoms included dizziness, sleepiness and anxiety — symptoms that could hint at THC intoxication.

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Emergency services also tested the carbon monoxide (CO) levels at two of the affected people's homes and at the restaurant, to see if CO poisoning was a possible culprit, but the tests came back negative. In addition, one of the affected individuals contacted PHMDC from the emergency department after testing positive for THC "without having knowingly consumed THC," the report noted.

PHMDC launched an investigation and contacted the restaurant's owner, who immediately agreed to close as the inspection commenced. The owner also informed the health department that the restaurant's building had a shared industrial kitchen where other vendors prepared food and products.

One of those businesses included a state-licensed vendor who prepares edibles containing THC derived from hemp — specifically delta-9 THC, which is the most abundant form of THC found in cannabis plants. Among the THC products was a cooking oil infused with the psychoactive ingredient.

It turned out that, on Oct. 22, the restaurant had run out of cooking oil and used oil from the shared kitchen in the building to prepare dough.

"The owner initially thought the oil was plain canola oil but later realized it might have been infused with THC," the report said. "Oil from a large, labeled storage container in the same area where the owner found the oil he used, tested positive for THC."

Ultimately, it was determined that the restaurant's customers were unintentionally exposed to THC, and no criminal charges were pursued, the report added. The restaurant reopened on Oct. 26 after being cleaned and sanitized, per Wisconsin Food Code.

Through further investigation, the health department identified 85 people who became intoxicated after eating food from the restaurant. Their ages ranged from 1 to 91 years old, including eight children and teens under 18 years old.

The individuals started experiencing symptoms within one to four hours of consuming pizza, garlic bread, cheese bread or a sandwich from the restaurant. Fifteen people tested positive for THC. For the other 70 people,THC testing either wasn't performed or the results weren't available.

Thirty-three of the people affected consulted a health care provider, mostly at hospital emergency departments, and three were hospitalized for at least one night. None of the children or teens were hospitalized. (Even relatively low doses of THC can put young kids at risk of serious side effects — including dangerously low blood pressure, coma, respiratory depression and seizures — but none of those symptoms occurred in this case.)

"Respondents were asked to provide the names of other persons who ate food from the restaurant and became ill; eight additional persons who became ill after eating at the restaurant were identified, but none completed a questionnaire," the report noted. That would bring the total to 93, assuming the eight additional people met the criteria for THC intoxication.

"Co-location of food establishments with businesses that make THC-infused products increases the risk that a THC-containing ingredient might be added to food, either intentionally or unintentionally," the report concluded. "Regulations regarding practices such as standard, clear labeling and locked storage for ingredients containing THC, might decrease the risk for unintentional THC exposure at licensed food businesses."