Food Safety Report: Multigrain Cheerios, Costco Wholesale, McGillivray Boulevard, Winnipeg, MB, Canada 2 years ago • details 2 Comments Comment Suspected food poisoning. Symptoms: Diarrhea, Stomach Pain Suspected source: multigrain cheerios Onset: Right away Duration: Less than 4 hours Sick: 2 people Additional information: There was a chuck of uncooked oats in the box.