Toronto’s public health department says a food poisoning outbreak at the Canadian National Exhibition was caused by a contaminated topping put on cronut burgers.

An investigation into the outbreak that sickened more than 220 people last week found samples of the cronut burger — a cheeseburger with a hybrid croissant-donut bun — were contaminated by a bacterium.

Officials say lab results show the staphylococcus aureus toxin — a recognized cause of food-borne illness — was found in the maple bacon jam put on top of the burgers.

The public health investigation is focusing on Le Dolci, the supplier of the bacon jam, to determine how the contamination occurred.

Public health officials say Le Dolci has stopped production of the product voluntarily and its food products will not be distributed until further investigation.