Testing has ruled out beef patties as the source of the outbreak of E. coli poisoning in the US that was linked to McDonald’s Quarter Pounders, the company says.

McDonald’s will resume selling the Quarter Pounder in the US this week.

The US Food and Drug Administration believed that slivered onions from a single supplier were the likely source of contamination, McDonald’s said on Sunday (US time).

As of Friday, the outbreak had expanded to at least 75 people sick in 13 states, federal health officials said.

A total of 22 people have been hospitalised, and two have developed a dangerous kidney disease complication, the Centres for Disease Control and Prevention said. One person has died in Colorado.

Early information analysed by the FDA showed that uncooked slivered onions used on the burgers “are a likely source of contamination”, the agency said.

McDonald’s has confirmed that Taylor Farms, a California produce company, supplied the fresh onions used in the restaurants involved in the outbreak, and that they had come from a facility in Colorado Springs, Colorado.

The 900 McDonald’s restaurants that normally received slivered onions from Taylor Farms’ Colorado Springs facility will resume sales of Quarter Pounders without slivered onions, McDonald’s said.

Taylor Farms said on Friday it had pre-emptively recalled yellow onions sent to its customers from its Colorado facility and continues to work with authorities as they investigate.

The outbreak involves infections with E. coli 0157:H7, a type of bacteria that produces a dangerous toxin. It causes about 74,000 infections in the US annually, leading to more than 2000 hospitalisations and 61 deaths each year.