Warm, dry weather hindered hundreds of firefighters battling a blaze in northern Colorado that federal officials say started with a camp stove.

The fire, which has grown to cover about 12 square miles, had prompted officials to evacuate about 80 homes, but all residents were allowed to return by Friday night.

Firefighters protected neighborhoods by burning grass, shrubs and small brush to prevent the wildfire from advancing toward homes. Crews got a boost as wind pushed the blaze to an area scorched by a previous wildfire, which slowed its growth.

The fire about 20 miles northwest of Fort Collins was almost half contained Friday evening. More than 500 firefighters, two planes and five helicopters were on hand to help fight the blaze that started Monday. No homes or buildings have been damaged. Three firefighters have suffered minor injuries.

The U.S. Attorney's Office said that James J. Weber of Fort Collins started the fire with an outdoor stove while camping in the Roosevelt National Forest.