By MATTHEW PERRONE AP Health Writer

WASHINGTON (AP) — Federal officials on Wednesday reported more cases of E. coli poisoning among people who ate at McDonald’s, as government investigators looking for the source of the outbreak identified an “onion grower of interest” in Washington state.

The Food and Drug Administration said 90 people in 13 states were sickened by the outbreak, up from 75 late last week. The number of hospitalized people increased by five, to 27 people. One death was linked to the outbreak.

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

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

More than 80 percent of people with E. coli interviewed by government investigators reported eating McDonald’s products containing fresh-cut onions, the FDA noted.