An E coli outbreak that resulted in at least one death has been linked to McDonald’s “Quarter Pounder” hamburgers, US public health authorities said on Tuesday.

The US Centers for Disease Control and Prevention said that there have been 49 cases in this discount sandwich-related outbreak which spans 10 states. Ten people have been hospitalized in this onset of cases.

“This is a fast-moving outbreak investigation. Most sick people are reporting eating Quarter Pounder hamburgers from McDonald’s and investigators are working quickly to confirm which food ingredient is contaminated,” the CDC said.

The agency noted that “McDonald’s has pulled ingredients for these burgers” and they won’t be available for purchase in some states. Most of the people who have fallen ill are in Colorado and Nebraska, officials said.

The agency said that McDonald’s is working with investigators to figure out which ingredient is making people fall ill. The company has stopped using “fresh slivered onions” and 1/4 lb beef patties in some states while the probe is ongoing.

The symptoms of E coli include extreme stomach cramps and diarrhea, as well as vomiting. The onset of symptoms is typically three or four days after ingesting the bacteria.

The majority of people recover without treatment within five to seven days. However, some people can develop severe kidney problems and require hospitalization, the CDC said.

McDonald’s said in a message on its website that safety is “our top priority and something we’ll never compromise on” and that as such, “it is why we are taking swift and decisive action following an E coli outbreak in certain states”.

The company said that preliminary findings indicate that a “subset of illnesses” might be associated with the slithered onions, made by one supplier that provides the allium to three distribution centers. All the local restaurants have been told to take the item off their menu and the company has temporarily stopped the distribution of slivered onions around the affected region.

The company is temporarily taking off the Quarter Pounder from restaurants in areas such as Colorado, Kansas, Utah, and Wyoming, and parts of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma.

McDonald’s also said it’s working closely with suppliers to ramp up supplies for the Quarter Pounder but “in the meantime, all other menu items, including other beef products (including the Cheeseburger, Hamburger, Big Mac, McDouble and the Double Cheeseburger) are unaffected and available”.

The news comes on the heels of former president Donald Trump appearing at a Pennsylvania McDonald’s in a staged campaign stop. Trump served french fries and spent a few minutes behind the frier in an attempt to mock Kamala Harris, who worked at McDonald’s during college; he has claimed, without evidence, that she did not work at the fast food restaurant.

This burger outbreak is among a host of recent incidents involving infected food. Some 12m lbs of meat was recalled earlier this month for possible listeria contamination.

Late this summer, dozens were sickened, and several died, from a listeria food poisoning outbreak tied to Boar’s Head deli meats.