Public safety officials say a deadly fire at a Waterville apartment building last week was caused by improperly discarded smoking materials.

The fire broke out in the early morning hours at Elm Towers on Elm Street on May 22. A resident, 65-year-old Ronald Kennerson, died in the fire. Three others were injured.

On Wednesday, a spokesperson for the Maine Department of Public Safety said the fire has been ruled accidental.

The Kennebec Water District put out a “Do Not Drink” order after firefighting foam was found to have entered the water supply when fire crews battled the blaze. The order was lifted a day later.