Fire raged through the historic Irving Junior High School on Thursday for the second time in less than six months.

Flames erupted in a stairwell about 5 p.m. in the building's west wing, 1200 E. 2100 South. The fire, believed to have been intentionally set, burned upward, damaging classrooms on the second floor and gutting the third floor, Salt Lake Battalion Chief Gordon Nicholl said.The west wing was the only section of the 72-year-old school not destroyed in a fire in November. Investigators suspect the first blaze also was set.

"It looks like the same story here," Nicholl said. "Somebody really likes to set fires in there."

Firefighters have doused several small blazes in the school since the general-alarm fire in November. All of them were intentionally set, Nicholl said.

Officials may consider ordering a demolition of the school if investigators determine it poses a significant hazard to residents living nearby, Nicholl said. "We'll be doing a lot of investigation here. If it's not safe for citizens, we can order a demolition."

Thursday's two-alarm blaze kept more than 45 firefighters busy for several hours. A heavy, white column of smoke filled the sky over the school and dozens of bystanders watched flames blacken third-floor windows.

Firefighters, who had the fire under control by 5:50 p.m., searched during the first minutes of the blaze for a security guard who had lived in an apartment on the third floor. But the firefighters later learned that the man no longer was living or employed at the former school building, which is owned by several people. The primary owner is the Horman family, Nicholl said.

The school's southeast gymnasium, east and central wings were gutted during the November blaze that caused $500,000 damage. Explosions during the fire leveled several walls.

Nicholl said extensive remodeling throughout the building was completed before the November fire, and "it appeared the owners were about to close a deal to sell the building."

The battalion chief said early Friday the latest fire caused about $10,000 damage.

"But I think the owners were going to sell the building for about $1.8 million before the fire in November," Nicholl said Thursday.

Thursday's blaze moved quickly through the school because open stairwells in the west wing acted like "perfect chimneys" - feeding air into the flames, Nicholl said.

The building, sold by the Salt Lake City Board of Education in 1977, was remodeled at a cost of $3.5 million.

Nearly all of its floors were hardwood, and the ceilings were 12 feet high. The renovation preserved the original architectural details.

"There was some beautiful woodwork in there - very ornate," Nicholl said.