According to the Centers for Disease Control and Prevention (CDC), a McDonald’s sandwich is making people sick in the US.

E. coli, a type of bacteria that can cause serious stomach problems, has been found in McDonald’s Quarter Pounder sandwiches, the CDC announced Tuesday.

So far, the CDC has recorded 49 cases of illness in 10 states. In ten cases, patients were hospitalized and one person died.

According to the CDC, most cases were recorded in the western and midwestern states.

The fast-food restaurant is working with investigators to determine which ingredients caused the outbreak, according to a statement from the CDC.

“McDonald’s has gathered ingredients for these burgers and they will not be available for purchase in some states,” the agency said.

“It is not yet known which specific food ingredient is contaminated,” the CDC added, noting that McDonald’s has already “discontinued the use of fresh-cut onions and quarter-pound beef patties in several states.”

The CDC said the sliced ​​onions are believed to be the likely source of contamination, and Food and Drug Administration (FDA) investigators are working to determine if the onions were sold to another company.

No recalls have yet been issued by the CDC or other health and food regulators.

The first case was recorded on September 27, researchers say. The victims range in age from 13 to 88 years old.

Of the 10 people taken to hospital, one person developed haemolytic uremic syndrome, a serious condition that can cause kidney failure.

Another person, whom the CDC described as “an older adult in Colorado” died after eating at McDonald’s.

Cases have been reported in Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin and Wyoming.

Shares of McDonald’s fell about 9% on the New York Stock Exchange after the news broke on Tuesday.

In a statement, McDonald’s said a preliminary investigation found “that some of the illnesses may be associated with chopped onions used in the Quarter Pounder that come from a single supplier serving three distribution centers.”

The Chicago-based company added that it has ordered all local restaurants to “remove this product from their offerings” and has halted shipments of sliced ​​onions to the region.

The sandwich is also being temporarily removed from menus in several states, the company said, adding, “We take food safety very seriously and it is the right thing to do.”

Other beef products will remain on the menu, McDonald’s President Joe Erlinger said in a video message.

“At McDonald’s, you can count on us to do the right thing,” he said.

E. coli is a diverse group of bacteria that normally live in the intestines of humans and animals.

While many are harmless, some produce toxins that can make you sick.

Symptoms include severe and sometimes bloody diarrhea, stomach cramps, vomiting and fever.

It usually takes a few days after you are infected for symptoms to manifest.

This isn’t the first E. coli outbreak to hit McDonald’s in recent years.

In 2022, six children in Alabama became ill with E. coli after eating chicken McNuggets.

Four children were hospitalized. Health inspectors later visited the affected restaurant and found several violations, including improper hand washing and a lack of gloves.