Costco discovered the source of its E. coli outbreak - and now there's a recall affecting Safeway, Walmart, and Starbucks

The source of a an E. coli outbreak spanning seven states has been traced back to a single ingredient in Costco's rotisserie chicken salad: diced celery.

The tainted ingredient came from Taylor Farms Pacific of Tracy, California, according to the FDA.

The supplier has since issued a recall for items that may contain its celery. The recall affects a nearly a dozen retailers including 7-Eleven, Safeway, Walmart, Sam's Club, Target, and Starbucks.

The strain of E. coli found in the celery is more dangerous than the outbreak tied to Chipotle, because it can lead to kidney failure, according to the Centers for Disease Control.

So far, 19 people have been infected with E. coli in California, Colorado, Missouri, Montana, Utah, Virginia, and Washington.

Five people have been hospitalized, and two have developed hemolytic uremic syndrome, a type of kidney failure. No deaths have been reported.

The CDC said most of those infected had eaten Costco's rotisserie chicken salad in the week before they became ill.

Consumers who purchased rotisserie chicken salad from any Costco store in the US on or before November 20, 2015, should not eat it and should throw it away, the CDC said.

Costco has removed all remaining rotisserie chicken salad from all stores in the US and stopped further production of the product until further notice.