The 5,200-acre Mercer Canyon fire in the rugged mountains west of Utah Lake has managed to barely stave off containment for three days, tying down about 200 fire fighters, vehicles and supporting aircraft.

Today crews went on the offense, venturing into the steep and rocky terrain to "burn out" remaining pockets of fuel, says Bureau of Land Management Spokeswoman Teresa Rigby.

Why? A change in the weather is threatening to give the fire a chance to flare up. The air temperature is rising, while moisture levels are dropping, Rigby says.

"The nighttime humidity is not good. You count on that to dampen things down," he says.

Meanwhile, the wind is threatening to kick up to provide the fire with oxygen.

On Sunday, that northern wind helped save the community of Saratoga Springs, which lies just north of the fire, by turning the blaze back on itself.

At risk in a flare up would be communications towers on the ridge tops, Rigby says.

Meantime, the Forest Service confirmed today that two firefighters were injured when their Roosevelt Duchesne District engine rolled in the Ashley National Forest 2:30 pm on Tuersday near Moon Lake.

There firefighters were airlifted to the University of Utah Medical Center in Salt Lake City for non-life threatening injuries.