BOULDER, COLO.—Firefighters made progress Sunday in battling a small wildfire that forced people to flee hundreds of homes in the mountains just outside downtown Boulder, Colorado, and authorities said they believe the blaze may have been human-caused.

Light winds pushed the flames in the wooded area a couple of miles west of Pearl Street, the shopping and dining hub in the heart of the university city. Crews contained roughly half of the fire that had burned just over 60 acres, but officials worried that stronger gusts that could fan the flames might develop overnight.

The Boulder Office of Emergency Management said 426 homes were evacuated before dawn and residents of an additional 836 were warned to get ready to leave if conditions worsened. The evacuation orders will remain in place overnight, said Boulder County Sheriff’s Cmdr. Mike Wagner.

There were no reports of injuries or damage to homes, emergency officials said. Several aircraft were dropping water and retardant on the flames, and a community centre opened as an evacuation shelter.

The fire started in the Sunshine Canyon area, which is dotted with a mixture of expensive homes and rustic mountain residences.

Boulder County Sheriff’s Cmdr. Mike Wagner said the area is used by hikers and for camping, leading authorities to believe the blaze was human-caused. Wagner said officials ruled out any lightning strikes or downed power lines.

Wagner said fire crews will monitor the blaze overnight and focus on full containment and mop-up on Monday.

Seth Frankel, who was warned that he and his family may need to evacuate, said he had packed up “generations of things” that can’t be replaced and was ready to go if the air quality got worse.

He said smoke was pouring toward neighbourhoods and many dead trees were combusting and sending black smoke into the air less than a half-mile from his home. But he and his wife, a Boulder native, and three daughters have dealt with fires and floods before.

“It’s always alarming and always on your mind, but it’s not an uncommon sensation around here,” said Frankel, who has lived in Boulder for 20 years.

In 2010, a wildfire destroyed nearly 200 houses in the mountainous area west of the city, home to the University of Colorado, Boulder.

Frankel got word of the fire early Sunday from a neighbour who received a warning call, and he was outside with neighbours watching the flames and smoke. But he let his daughters, 9, 11 and 13, sleep in.

“It’s still alarming, but there’s no panic,” Frankel said. “We will be long since gone when parents are no longer smiling.”