Firefighters have made significant strides in a wildfire that has consumed more than 21 square miles of forest and grazing land on the Navajo Nation.

Fire officials say crews were able to contain 20 percent of the Assayii (UH'-say-eye) Lake Fire by Thursday night thanks to less windy weather.

Crews took advantage of light winds to mobilize air drops of water and fire retardant.

Officials say the fire was also slowed by reduced vegetation.

The blaze has destroyed at least five structures and 50 homes are still threatened.

Authorities say the human-caused fire has forced some families to evacuate their sheep camps in the Chuska Mountains, just east of the Arizona-New Mexico border.

Firefighters say they plan to keep the fire from burning southward by continuing to remove vegetation.