(NEXSTAR) – A salmonella outbreak that has been traced to 37 states across the country is being caused by fresh whole onions, the Centers for Disease Control and Prevention (CDC) said in an update Wednesday.

“Throw away any unlabeled onions at home,” the CDC said in a tweet. “Do not eat, sell, or serve red, white or yellow onions imported from Mexico and distributed U.S.-wide by ProSource Inc.”

The company imported the onions from Chihuahua, Mexico, and distributed them to restaurants and grocery stores throughout the United States. ProSource said the possibly tainted onions were last imported Aug. 27, but because of the vegetable’s long shelf life they may still be on shelves.

Investigators are still working to determine if the outbreak is tied to other distributors.

This is a developing story.