Erratic winds have blown up the Cow Creek fire in the backcountry of Rocky Mountain National Park to at least 1,500 acres, forcing the closure of a ranch road and leading fire bosses to keep firefighters off the front lines.

Park officials said early Saturday evening that while there hadn't been a lot of growth in the fire through the day, better mapping provided a more accurate estimate of the size of the blaze.

While air tankers dumped 10,000 gallons of water along with six drops of retardant on the flames Friday afternoon, the gusty winds forced firefighters on the ground to pull back for their safety, park officials said.

Although better weather conditions for fighting the blaze were forecast for Saturday, the day's plan was to attack the flames from the air and keep line crews away due to the erratic nature of the fire, park spokeswoman Kyle Patterson said. The priority will continue to be defensive fire operations and structure protection for the community of Glen Haven, she added.

As the fire spread to the west, north, and northeast, a decision was made Friday evening to close the McGraw Ranch Road to the public so it could better handle firefighting traffic. Residents in the area so far were not being asked to leave their homes. Park staff also closed the North Fork Trail inside the park as a precautionary measure.

Rangers headed onto the trails in the North Fork drainage Friday evening to contact backcountry travelers, and 24 hikers were brought out. Ms. Patterson said the Cow Creek Trail and North Boundary Trail were closed along with the Dunraven/North Fork trail as precautionary measures.

The blaze, burning in a lodgepole forest, was spotted Thursday about 1 mile south of Mount Dickinson near the northern edge of the park. It's now thought that lightening sparked the fire.

Although burning in the backcountry and naturally caused, the decision to fight the fire rather than to let it burn naturally was made because "of other fires in the state and available resources, weather forecast of high winds and low humidity, as well as the proximity to the community of Glen Haven," park spokesman Kyle Patterson said.

The area, about 7 miles from the nearest road, is heavily timbered, and some of the trees had been killed by mountain pine beetle infestations, which have plagued other parts of Rocky Mountain.