WASHINGTON – U.S. federal officials reported more cases of E. coli poisoning among people who ate at McDonald’s, as government investigators seeking the outbreak’s source identified an “onion grower of interest” in Washington state.

The Food and Drug Administration on Wednesday said 90 people across 13 states have fallen ill in the outbreak, up from 75 at the end of last week. The number of people hospitalized increased by five, to 27 people. One death has been tied to the outbreak.

Officials have said raw, slivered onions on McDonald’s Quarter Pounder hamburgers are the likely source of the E. coli. McDonald’s said the onions came from a single supplier, the California-based Taylor Farms. The company has since recalled the yellow onions it sent to McDonald’s and other restaurant chains.

The FDA said Wednesday it has begun inspecting Taylor Farm’s processing centre in Colorado Springs as well as an “onion grower of interest” in Washington state. It did not name the grower.

More than 80 per cent of people with E. coli interviewed by government investigators reported eating McDonald’s items containing fresh, slivered onions, the FDA noted.

Chris Kempczinski, McDonald’s chairman, president and CEO, apologized for the outbreak Tuesday on a conference call with investors. He said it was the first major public health issue tied to McDonald’s in more than 40 years.

“Nothing is more important to us than the safety of our customers,” Kempczinksi said. “The recent spate of E. coli cases is deeply concerning, and hearing reports of how this has impacted our customers has been wrenching for us.”

“I’m relieved that this situation appears to be contained and I remain confident in the safety of eating at McDonald’s,” Kempczinski said.

Still, the company acknowledged that the outbreak hurt its sales momentum. The company didn’t share sales data, but Placer.ai, which tracks retail traffic using cell phone data and other signals, said it saw a 9 per cent year-over-year decline in U.S. visits to McDonald’s at the end of last week.

Kempczinski said the company hopes to win back customers by acting swiftly to contain the outbreak, cooperating with authorities and promoting its offers, but it will take further actions if necessary, he said.

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