(Gray News) – At least one person has died and dozens of others have been sickened by E. coli linked to McDonald’s Quarter Pounders.

An investigation into the illnesses began Tuesday, according to the Centers for Disease Control and Prevention.

The CDC said 49 people from 10 states have become ill, with about half of them from Colorado.

One elderly person in Colorado has died and 10 people have been hospitalized.

The CDC said everyone they interviewed reported eating at McDonald’s before their illness started, specifically eating a Quarter Pounder hamburger.

The specific ingredient in the Quarter Pounders that was contaminated with E. coli is still unknown, but researchers have narrowed it down to the chopped onions or the beef patties.

McDonald’s has removed the onions and beef patties from restaurants in the affected states. As a result, Quarter Pounders may be temporarily unavailable in some states.

McDonald’s said the beef patties and onions are only used on Quarter Pounders and not on other menu items.

As of Tuesday afternoon, the confirmed illnesses have been reported in the following states:

• Colorado: 26 people
• Nebraska: 9 people
• Utah: 4 people
• Wyoming: 4 people
• Iowa: 1 person
• Kansas: 1 person
• Missouri: 1 person
• Montana: 1 person
• Oregon: 1 person
• Wisconsin: 1 person

The first case was reported on September 27. The CDC said many illnesses may not yet have been reported because it usually takes a few weeks to determine whether a sick person is part of an outbreak.

The actual number of sick people in this outbreak is also likely much higher than the reported number, the CDC said.

McDonald’s corporate headquarters issued the following statement late Tuesday:

Most people infected with E. coli experience severe stomach cramps, diarrhea (often bloody), and vomiting.

According to the CDC, symptoms usually begin three to four days after ingesting the bacteria. Most people recover without treatment after five to seven days.

The CDC urges anyone with symptoms of an E. coli infection after eating at McDonald’s to contact their doctor and report what they ate.

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