Three people have died and three others have been hospitalized after drinking milkshakes contaminated with Listeria bacteria from a restaurant in Tacoma, Washington, health officials say.

Investigators found the outbreak was linked to ice cream machines that were not cleaned properly at a Frugals restaurant, according to a release from the Washington State Department of Health. Listeria can affect people up to 70 days after consumption and the machines were used through August 7, the release said.