Investigators were still trying to determine late Saturday the cause of an afternoon fire that injured six Salt Lake firefighters and heavily damaged a west-side warehouse.

One firefighter suffered a broken leg while connecting a hose to a hydrant and five suffered heat and smoke exhaustion while battling the fire in mid-90-degree temperatures. A Holy Cross Hospital emergency room nurse said the six, whose names were not released, were treated in the emergency room Saturday evening.Ten fire engines, including one from Salt Lake County's Fire Division, and 65 firefighters battled the 3:24 p.m. blaze at the Kero-Sun Sales and Service building, 530 W. Second South, for more than an hour before bringing it under control. Firemen were still putting out hot spots several hours later.

The fire destroyed the front section of the building, where wooden doors, lumber and hardware were stored, but was prevented from spreading to an appliance storage area in the rear section of the warehouse.

Kirby Forbush, controller for Rio Grande Building Products Inc., which owns the building, estimated damage at between $100,000-$200,000 in inventory. The front section of the building was destroyed, but a dollar damage estimate on the structure was unavailable.

Had the blaze spread to the appliance storage area, the loss could have been twice or three times as high, he said. The rear section received only water damage.

"We'd been doing inventory counts," Forbush said, "and I was coming out of the company building next door when I saw three or four cars stopped and the people staring. I walked around to see what they were looking at and saw flames leaping up." Kirby called in the report on the four-alarm blaze.

Ten of Salt Lake City's 13 fire stations responded to the alarm, but fire-fighters found the front of the building fully engulfed when they arrived, said Salt Lake Fire Battalion Chief Don Hill.

Firefighters dug a trench between the two sections of the building to prevent the fire from spreading to the rear section. More than 2,750 gallons of water a minute were pumped on it for nearly 90 minutes before the blaze was contained.

A fire investigator said it could take as long as several days to determine how the blaze started.

The fire, which sent flames 30 feet in the air, stretched fire protection for Salt Lake City critically thin because other units were battling local brush and grass fires Saturday, he said.

"We've got three units, including one at the airport, to cover the city right now," Hill said. `South Salt Lake is helping cover for us in case something else happens while we're here.

"The front end of the building was completely engulfed; it's a total loss," he said, "but Salt Lake City itself could have had a lot worse fire with all these tall buildings."