High winds are keeping ground crews and helicopters from fighting the Fern Lake Fire in Rocky Mountain National Park.
    
Park officials say the wind threatened to topple trees and made flying conditions unsafe Friday, so firefighters were moved off the fire line and helicopters were grounded.
    
The fire has charred nearly 2½ square miles. Containment was listed at 40 percent Friday.
    
The National Weather Service has issued a high wind warning in effect until 11 a.m. Saturday, with sustained winds up to 45 mph and gusts up to 75 mph possible.
    
The fire started Oct. 9. The cause is still under investigation.