A ceiling light bulb that exploded and rained smoldering debris onto pallets of padding material was cited Friday as the cause of a fire that did an estimated $25,000 damage inside a massive storage warehouse on Naperville's far west side.

Members of the Naperville Fire Department's investigation team drew that conclusion about the blaze that erupted at 11:30 p.m. Thursday inside the 100,000-square-foot Prager Moving & Storage Co. facility at 155 Fort Hill Drive, Assistant Fire Chief Rich Mikel said.

A firefighter who sustained a minor injury after slipping and falling on ice in a parking lot was the only person hurt during the incident. He was released after undergoing treatment at Edward Hospital in Naperville, Mikel said Friday evening in a written statement.

The light bulb disintegrated above a loading dock area at the building's northwest corner. Mikel said blanket-like padding material used by company truck drivers and movers during their daily duties caught fire directly beneath the shattered bulb, with the flames eventually activating the warehouse's automatic sprinkler system and triggering its fire alarm.

Acrid, white smoke had filled the facility by the time firefighters arrived at the scene four minutes after the alarm sounded, Mikel said. Twenty-five firefighters and 10 emergency service vehicles were ultimately sent to the warehouse.

The flames were confined to the loading dock area and damaged several pallets of electrical equipment in addition to the padding material, Mikel said. The warehouse was built with two large ceiling-rooftop electrical fans, which firefighters switched on to ventilate smoke from the building.

Mikel said the fire "demonstrates the tremendous value of a properly designed, properly working fire sprinkler system."

"Had this building not had a properly functioning sprinkler system, damage to the contents would have been significantly higher, the building itself would have likely received extensive damage and fire suppression efforts would have been much more complicated," Mikel said.

The blaze was extinguished at 12:30 a.m. Friday, although firefighters remained at the scene until 1:45 a.m., performing clean-up operations.

Prager has been in business since 1954 and employs 75 people, according to the company's Web site. The business was closed for the night and no workers were on the premises when the fire erupted.