A suspected poisoning at a Markham eatery sent 4 to ICU. Experts think they've found a culprit

A suspected poisoning at a Markham, Ont., restaurant has left at least 12 people seriously ill — with four of those needing intensive care in hospital — and the culprit could be a substance sometimes used in traditional Chinese medicine, according to health experts.

Dr. Barry Pakes, medical officer of health for York Region, told CBC Toronto on Tuesday that all of the patients who fell ill after eating at Delight Restaurant & BBQ on the weekend are "doing well" and are expected to recover.

York Region Public Health's investigation is ongoing, and no firm conclusions can yet be drawn about what exactly caused them to become sick, Pakes said. But their symptoms point to the possibility that they ingested aconite, sometimes called wolf's bane or the queen of poisons, which is derived from a particular genus of plants.

The substance affects nerves that control muscles in the body, leading to numbness in the face and extremities, severe gastrointestinal distress and, in some cases, an irregular heartbeat. Ingested in large enough quantities, aconite can induce fatal arrhythmia of the heart.

LISTEN | Dr. Barry Pakes on York Region's ongoing investigation:

Dr. David Juurlink, head of clinical pharmacology and toxicology at the University of Toronto, said symptoms usually begin within minutes or hours of ingesting aconite. Juurlink has not personally treated any of the people who became ill in this instance, but he said he has spoken directly to colleagues who have. The patients all seem to have eaten a chicken dish at the restaurant, he said.

York public health is currently testing various samples taken from the restaurant, which has been closed for the time being. Pakes said the owners are fully co-operating with the investigation, and that there has been nothing to suggest the poisoning was intentional.

He pointed to a recent case in British Columbia in which aconite was mistakenly mixed into ground ginger root. The two substances look similar.

Pakes said he expects to have further updates for the public later today or in the coming days, at the latest.

Anyone who dined in or ordered takeout or delivery is asked to throw out any food from the restaurant.