TRUCKEE (AP) — Nevada County prosecutors have filed manslaughter charges against a Truckee-based contractor whose negligence they say produced the carbon monoxide that killed two men at a home north of Lake Tahoe last fall.

Assistant District Attorney Anna Ferguson said 41-year-old Kurt Schoemig was charged Monday with two counts of involuntary manslaughter.

She said in a statement he “played a substantial factor” in causing the deaths of 69-year-old Albert Senzatimore of San Jose and 57-year-old Gary Trovinger of Los Gatos at Trovinger’s home in Tahoe Donner in October.

Ferguson said Schoemig, president of Cedar Ridge Builders, didn’t have the necessary permit for work done last year.

Police say an employee cut a furnace exhaust pipe, but the project wasn’t completed, leaving the pipe to vent into the home when the heater started.