All signs point to the potato salad — or more likely one of the raw ingredients that goes into it — as being the cause of the E.coli outbreak that sickened some 60 people on the Fond du Lac Reservation in July.

According to word from Doug Schultz, spokesperson for the Minnesota Department of Health, on Wednesday, the investigation has revealed that the illness came from three separate events, the Elders’ Picnic, a private wedding and a three-day conference. All were held on the reservation between the dates of July 11-16, and all were catered by the same entity.

“After interviewing a good percentage of the people involved,” said Schultz, “there are clear indications that the potato salad was the likely vehicle for the illness,” which he added came from the O157 strain of E.coli — one of the most common forms.

The investigation unveiled, however, that potato salad was only served at two of the three events, which leads investigators to suspect one of the raw products that goes into the salad, such as celery or onions.

“We haven’t yet been able to definitely prove just what that was,” said Schultz. “At first, we thought it was the celery, but we were unable to find any pathogens on the celery we tested.”