Hugh Hefner's famous California bachelor pad was dragged into an investigation by the Los Angeles County Health Department after it played host to a fundraiser as part of the Domainfest conference.
Many guests allegedly fell ill with a respiratory condition and over 120 people suffered a fever.
Authorities have now traced the illness to a strain of legionella bacteria, which causes Legionnaires' disease, allegedly found in a hot tub at the Playboy Mansion, according to the Los Angeles Times.
The findings were presented at a conference on Friday at the Centers for Disease Control in Atlanta, Georgia.
A spokesperson for the publishing mogul previously denied reports that a fog machine used at the party had spread the sickness.