The fire that burned Oquirrh Elementary School and displaced 900 students ignited near a north-end bookshelf and counter space, fire officials say.
Investigators, including a federal Alcohol, Tobacco and Firearms task force, have finished their work at the scene and released the burned-out structure to the Jordan School District Thursday.The cause of the four-alarm fire remains unknown, however.
"Whether it started with roof tile and dropped down on the bookcase, or started in those shelves and went up is undetermined at this point," West Jordan Deputy Fire Chief B.J. Snooks said.
Investigators have ruled out any possibility of arson and consider the blaze accidental.
Oquirrh Elementary, 7165 S. Paddington Drive, (3285 West), is one of several Salt Lake Valley schools designed with an "open environment." The concept allows for a large, open space partitioned into classrooms by using filing cabinets and other dividers in place of traditional walled classes.
The design has come under scrutiny by those concerned with its safety in circumstances like Saturday's fire.
"Obviously, it contributed to the spread," Snooks said of the open-space design. Fire moved more quickly through the building with no walls to block it. However, there are other positive aspects to such a design, he said.
If the fire occurred on a school day and with a large open area such as Oquirrh's, someone likely would have smelled smoke and spotted the fire sooner.
"If someone was in there, then the open classroom would help monitor (fire danger)," he said. "If it had been a closed classroom (with traditional walls), it might have been a while before someone smelled the fire."
Two girls were spotted in the area of the fire Saturday afternoon. Fire officials want to speak with the teens simply for details that could help determine what started the blaze, Snooks said.
"They were up close to the buildings," he said. "We just wanted to know what they saw. We're absolutely sure they did not enter the school or throw anything in that would have started the fire."
Forensic investigation may be required to find out exactly what caused the multimillion dollar blaze.
"Something in that area started it," Snooks said. There were electrical and ordinary combustible items stored in the area of the bookcases and cupboards.
"We're not ruling out that someone left something there that was warm," he said.
Heat from a fire in the area of the bookcases Saturday penetrated the school's tile ceiling and heated up the metal roof, igniting the tar sealant.
"Then you get two fires, one on the inside, one on the outside," Snooks said.
"The heated gas and smoke from these shelves are going straight up . . . and heating up the metal roof at that point," he said. "It's deflecting all that heat between the roof and the ceiling.
"The roof . . . hits its ignition point," he said. "That's the first indication anyone sees of the flames on the outside."
At that point, the fire in the area of the bookcase spread, and onlookers spotted puffs of smoke emerging from between the exterior bricks. The school's heat alarm sounded.
"With the fire load, it's now just going to spread," he said.
The area of the bookshelves was also one of cupboard storage, crammed with paper material, according to Snooks.
"What's stacked on that counter top, we're not sure right now," he said. "It could be that something ignited the ceiling tile and that fell down onto those papers."
Saturday's fire burned for more than three hours, initially shooting flames some 50 feet high and blanketing the valley in heavy smoke. The school is a total loss. Damage was initially estimated near $6 million, but has since been dropped to about $4.5 million, Snooks said.