DENVER (AP) — E. coli food poisoning linked to McDonald’s Quarter Pounder hamburgers has sickened at least 49 people in 10 states, including one person who died and 10 who were hospitalized, federal health officials said Tuesday.

The death was reported in an older person in Colorado, and one child has been hospitalized with severe kidney complications, the U.S. Centers for Disease Control and Prevention reported.

Infections were reported between Sept. 27 and Oct. 11, in Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin and Wyoming. Colorado has the most cases, 26, followed by Nebraska with nine.

Everyone interviewed in connection with the outbreak had reported eating at McDonald’s before falling ill and most mentioned eating Quarter Pounder hamburgers, the CDC said. The U.S. Agriculture Department, the Food and Drug Administration and state health officials are also investigating.

A specific ingredient has not been identified as the cause, but investigators are focused on onions and beef. A preliminary FDA investigation suggests that slivered onions served on the burgers are a likely source of contamination. The USDA is investigating the hamburger patties.

In a statement, McDonald’s officials said that initial findings suggest that some illnesses are linked to onions sourced from a single supplier. The company has halted distribution of the slivered onions and temporarily removed the Quarter Pounder from menus in the affected states, and also in portions of Idaho, Nevada, New Mexico and Oklahoma.

“We take food safety extremely seriously and it’s the right thing to do,” the statement said.

E. coli bacteria are harbored in the guts of animals and found in the environment. Infections can cause severe illness, including fever, stomach cramps and bloody diarrhea. People who develop symptoms of E. coli poisoning should seek health care immediately and tell the provider what they ate.

The news comes in an already tough year for the Chicago-based McDonald’s chain. Its global same-store sales fell for the first time in nearly four years in the second quarter as inflation-weary customers skipped eating out or chose cheaper options. The company responded with a $5 meal deal, which was introduced at U.S. restaurants in late June and was recently extended through December. The deal doesn’t include the Quarter Pounder.

McDonald’s shares dropped 9% in after-hours trading Tuesday after the CDC’s announcement.

The type of bacteria implicated in this outbreak, E. coli O157:H7, causes about 74,000 infections in the U.S. each year, leading to more than 2,000 hospitalizations and 61 deaths. Infections are especially dangerous for children younger than 5 and can cause acute kidney failure.

BUENOS AIRES, Argentina (AP) — An initial toxicology report for ex-One Direction singer Liam Payne, who died last week after falling from a third-floor hotel balcony in Buenos Aires, showed that he had cocaine in his system after his death, an Argentine official said.

The final toxicology results are not expected to be made public for some weeks. But the preliminary toxicology report of the wildly famous boy band star, handed to local prosecutors on Monday, suggested evidence of exposure to cocaine, the official said, stressing that these initial results don’t offer an accurate reading of just how much was circulating in his blood when he died.

The official spoke on condition of anonymity because he was not authorized to brief journalists. The preliminary report was widely reported in local media on Monday.

Argentina’s public prosecution is investigating the case — which is not uncommon when a death is sudden or unexpected.

Payne’s autopsy concluded that the traumatic injuries that caused his death were consistent with his three-story fall from the hotel window. Prosecutors have ruled out anyone else being involved.

Argentine investigators found what appeared to be narcotics and alcohol strewn about broken objects and furniture in 31-year-old Payne’s hotel room, leading the public prosecution to surmise Payne had suffered a substance abuse-induced breakdown around the time of his fall. The prosecution said Payne could have plunged from his hotel room balcony in a state of “semi or total unconsciousness.”

Photos purportedly taken from inside Payne’s hotel room published by local media showed snowlike powder left on a table and a smashed-in TV screen. Police also discovered a blister pack of clonazepam, a central nervous system depressant, and over-the-counter medications scattered among Payne’s belongings. Shortly before Payne’s death, the hotel manager called 911 to report a guest acting aggressively and under the influence of drugs and alcohol.

Investigators are also trying to figure out who sold Payne the drugs he took at the CasaSur Hotel in Palermo, a chic neighborhood of the Argentine capital. Police have taken statements from at least three hotel employees, as well as two women who visited Payne’s hotel room a few hours before his death.

Fans and major pop industry figures around the world have reacted with an outpouring of grief.

The late singer’s father, Geoff Payne, was still in Buenos Aires meeting with the prosecutors and other local officials Monday in an effort to organize the repatriation of the remains.

Argentine authorities expect to release the body next week, clearing the way for Geoff Payne to fly home and hold a funeral back in England, where on Sunday hundreds of fervent One Direction fans gathered to mourn the musician.