The Salmonella Newport outbreak linked to red onions from Thomson International Inc., a supplier in California, has expanded to 869 cases in the U.S. and 339 cases in Canada. The number of confirmed cases has roughly doubled since we first reported on the outbreak on August 4. There have been 116 hospitalizations in the U.S., but no deaths.

On Wednesday afternoon, the FDA shared an uncommon “Urgent Recall Notification,” alerting customers of meal kit delivery company HelloFresh that one of the company’s suppliers had sourced onions from Thomson International. Anyone who received a delivery from HelloFresh containing onions between May 8 and July 31 is advised to throw it away. Customers are also advised to thoroughly clean any surfaces that might have come into contact with contaminated onions.

The recall has expanded in recent weeks to include cheese dip, salsas, and loose onions sold at Trader Joe’s in four Western states and Ralph’s in California. So far, sicknesses have only been linked to red onions, but the company has recalled sweet, white, and yellow onions as well because of cross-contamination concerns.

This is already one of the largest Salmonella outbreaks in U.S. history, and Thomson International appears to have supplied onions to many different customers during the period in which some product harbored Salmonella. It’s not yet clear how the onions were contaminated, or whether people have gotten sick from restaurant food, from home cooking, or both.

Onions that were shipped during the affected period may be particularly hard to trace because they have long shelf lives and many were chopped up for use in prepared foods. They appear to have reached HelloFresh after passing through another supplier, meaning they may have been difficult or impossible to identify at the company’s processing facilities.

We will continue to update this story as it evolves.