A fire that started on a second-floor porch Saturday night was caused by improper disposal of smoking materials. The fire was reported at 10:15 p.m., Saturday, at a multi-family home on 238 Walnut St., Fire Capt. Kevin Cavagnac said. When firefighters arrived, they found flames shooting from the porch and up the exterior siding and the porch roof, he said. They were able to extinguish the fire and prevent it from spreading into the walls or attic space so all residents were allowed to return to their apartments, Cavagnac said. The cause of the fire was investigated by the Holyoke Fire Department and State Police fire investigators, he said.