GRAND CANYON NATIONAL PARK, Ariz. (AP) _ Winds gusting up to 50 mph pushed a 10,000-acre wildfire down the northern rim of the Grand Canyon and away from more heavily forested areas beyond the national park.

The size of the fire, which started out as a 1,500-acre prescribed burn on April 25, grew on Tuesday, and the high wind prevented helicopters from fighting the blaze, officials said.

Western winds drove the flames over and down the canyon's North Rim and away from birch and fir trees to the north, said park spokeswoman Vicki Allred. It was not threatening any structures.

The blaze was 43 percent contained on Tuesday, she said. It burned about 1,000 feet below the rim before losing momentum as the number of trees dwindled. The South Rim of the Grand Canyon, the site where most tourists visit, remained open.

The Outlet fire was driven out of control by high wind a week ago. It was designed to help rejuvenate forested areas and prevent future wildfires.

About 900 firefighters and support personnel battled the fire Tuesday, and Allred said officials hoped for more. ``This remains a very dangerous fire, especially if the winds shift,'' she said.

Elsewhere in the state, firefighters were nearing full containment of a 9,359-acre wildfire in the Tonto National Forest in central Arizona east of Phoenix. The fire was 95 percent contained Tuesday and should be fully contained by tonight, said forest spokesman Jim Payne.

The number of firefighters was reduced to 36 as crews headed to the Grand Canyon and to New Mexico to battle fires, including the Los Alamos blaze that destroyed hundreds of homes.