Cardboard boxes blamed in Maine fire that killed 4 Dawn Gagnon / AP file Authorities respond to a fire on Dow Road in Orrington, Maine, Nov. 10, 2012. A pre-dawn fire that killed a 30-year-old man and his three children and hospitalized the mother was caused by empty cardboard pizza boxes stored too close to a wood-burning stove, Maine fire officials said Monday. The family likely used the boxes to help start the fire in the stove after they returned to their Orrington home from bowling late Friday night, fire investigators said. A container of lighter fluid found nearby probably accelerated the spread of the fire once the boxes stored outside the stove ignited and family members had gone to bed. Fire Marshal Joe Thomas called the fire a tragedy. It was the deadliest fire in Maine in 20 years. "It was purely accidental," Thomas said. Neighbors reported the fire about 2:30 a.m. Saturday after hearing Christine Johnson, 31, screaming from atop a roof above a breezeway between the house and a garage. Johnson remained hospitalized for smoke inhalation on Monday. The fire killed her husband, Benjamin Johnson III, along with their children: two boys, 9-year-old Ben and 4-year-old Ryan, and one girl, 8-year-old Leslie. The children were found in a second-story bedroom, and their father was found at the head of the stairs. They all died from smoke inhalation, according to the medical examiner's office. The home's furnace was not working, so the residence was heated with the wood stove and a propane heater placed inside a fireplace, officials said. The home had smoke detectors, but neighbors who rushed to the scene didn't hear them and investigators haven't determined if they were in working order, Thomas said. The town of Orrington has about 3,900 residents and serves as a bedroom community to Bangor, six miles to the north. The family moved from Bangor and into the rental house about six months ago. Benjamin Johnson worked at a Wal-Mart and as a part-time dealer at a casino in Bangor, neighbors said. Christine Johnson is an author who worked from home, Department of Public Safety spokesman Steve McCausland said. The fire was the deadliest in Maine since December 1992, when an 18-year-old man set fire to an apartment house in Portland, killing a baby and three adults. Virgil Smith, now 38, was convicted of four counts of murder and one count of arson. He is serving a 58-year sentence. Smith started the fire to get back at his ex-girlfriend, who lived in the building, but said he didn't intend to hurt anyone. With heating season upon Maine, Thomas said combustible items should be kept at least 3 feet from wood stoves and flammable liquids should never be used to start wood-stove fires. "The point we're trying to make is this type of thing doesn't have to happen," he said.