The FDA is investigating McDonald's supplier Taylor Farms as the source of the E. Coli outbreak

The Food and Drug Administration is investigating whether Taylor Farms, a supplier to McDonald's, is linked to quarter-pounder hamburgers with E. coli is the likely source of the outbreak, which has killed at least one person and sickened nearly 50 others.

In a notice to customers, distributor US Foods said Taylor Farms has announced a recall of four raw onion products out of an abundance of caution due to “potential E. coli contamination.” The notice urges consumers such as restaurants to stop using and destroy affected products as soon as possible.

The FDA and the Centers for Disease Control and Prevention have cited slivered onions served on hamburgers as a potential source of contamination.

An FDA spokeswoman confirmed Thursday that the agency is investigating Taylor Farms, adding, “We are looking at all possible sources.”

As of Wednesday, the outbreak linked to E. 49 people fell ill due to coli infection. One elderly adult died, and 10 others were hospitalized, including a child with hemolytic uremic syndrome.

Colorado restaurant chains including Illegal Pete's and Taco Bell also removed onions from their menus after the recall. A spokesperson for Yum! Brands, the parent company that owns Taco Bell, said Pizza Hut and KFC have also removed fresh onions from their menus at select restaurants. Associated with these restaurants e. No symptoms of cholera

Until now, it was unclear where McDonald's onions were sourced — neither the restaurant chain nor public health officials have publicly said where the onions were grown or whether they were shipped to other restaurants.

A McDonald's spokeswoman said Wednesday that the raw onions were sourced from a single supplier and processed at a single facility. they are It is broken into pieces.

A spokesperson for Taylor Farms did not immediately respond to a request for comment. Taylor Farms is a California-based producer of fresh-cut fruits and vegetables, according to the company's website.

The strain of E. coli in the outbreak, called O157:H7, produces a powerful toxin that can damage the lining of the small intestine.

Health officials said Wednesday they expect the number of cases to rise.

Meanwhile, McDonald's is already facing lawsuits.

On Thursday, Ron Simon & Associates, a food safety law firm, said it filed a second lawsuit, this time on behalf of Nebraska resident Clarissa DiBock, who said she bought a Quarter Pounder at a local McDonald's on Sept. 18. A few days later, DiBock became ill and was forced to seek treatment where he tested positive for O157:H7, according to the lawsuit.

the first the case Eric Staley, a Colorado resident from the firm, was on the side. Staley said he suffered gastrointestinal symptoms after eating a burger at McDonald's.

Ron Simon, the firm's managing partner, told NBC News that he now represents 15 families who claim damages, with patients ranging in age from their 20s to their 60s.

“They're in different states and in different communities with different results,” he said.