Spotters are planning to watch a 550-acre fire burning in the mountains west of Golden overnight, trying to determine whether to evacuate 350 homes in a nearby subdivision.

The blaze died down at nightfall but was still 0 percent contained.

The remaining seven fire agencies, a helicopter and an out-of-state crew from Idaho are expected to leave the site of the Indian Gulch Fire around midnight and return to work in the morning.

Swirling winds made the blaze unpredicatable and the rocky, roadless Mount Galbraith where it’s burning has left containment duties to ditch-digging hand crews and a single helicopter.

The blaze, first reported around 10:15 a.m., burns between Clear Creek and Golden Gate canyons, leaving Golden residents on alert and closing a section of U.S. Highway 6.

“It’s difficult to predict. They’re working it and watching it. It burns a little bit in this direction and then moves a little in that direction,” Jefferson County Sheriff’s spokeswoman Jacki Kelley said earlier today. “We’re still not ready to launch any evacuation. We may, but we’re not there yet.”

Up to 60 firefighters were on scene.

State transportation officials have closed U.S. Highway 6 between Colorado highways 119 and 93 because of the wildfire, which started around 10:15 a.m.

A Douglas County helicopter was dropping water on the blaze to unknown effect. A single engine air tanker that would have dropped fire retardant was grounded because of mechanical problems.

Fire engines were standing by in the nearby subdivision of Mountain Ridge, the closest to the wildfire, in case winds changed.

Residents in the unincorporated area around Golden received an emergency call early Sunday warning them to remain on guard, though no evacuations were ordered.

“Golden Police sent the reverse 911 call just in case,” Kelley said. “It’s pretty close.”

Kelli Arnold, 58, and her neighbors stood in the middle of her street in a nearby subdivision watching the smoke rise over the mountains.

Arnold said she wasn’t worried about the home she’s lived in for a decade.

“It’ll take a ways to get to us,” Arnold said.

Warm weather and high winds have upped fire danger across Colorado in recent weeks.

The National Weather Service issued a red flag warning for the Denver area for Monday, citing more strong winds, low humidity and abnormally warm temperatures.

“Fuels are reportedly quite dry, which will further contribute to the critical wildland fire danger anticipated on Monday,” the warning reads.

Staff writer Kyle Glazier contributed to this report. Jessica Fender: 303-954-1244 or jfender@denverpost.com.