JEFFERSON COUNTY — Fire crews from across the region tried to establish a perimeter overnight on a 3,000-acre Lower North Fork Fire in Jefferson County.

The blaze had burned several homes southeast of Aspen Park, near Conifer, and driven evacuees from more than 900 homes in the first major fire this season. The sheriff’s office said late Monday that it was investigating one fatality within the fire zone.

The fire was located between U.S. 285 and South Foxton Road; Pleasant Park Road, Oehlmann Park Road and south to Deer Creek Canyon.

“We have lost some homes now. … Could be more than five, could be more than 10, could be more than 20; we just don’t know,” said Jacki Kelley, a spokeswoman for the Jefferson County Sheriff’s Office.

At 9 p.m., there were 100 firefighters from across the region trying to establish a perimeter on the fire, and more personnel were to arrive overnight to assist, Kelley said.

“We are asking people to be ready tonight to leave if need be, even in the middle of the night,” Kelley said late Monday.

After crews battled wind gusts of more than 70 mph in the foothills Monday, calmer winds and the chance of a rain shower enter the forecast for the area today.

Several roads in the area remain closed because of flames, smoke and firefighting operations. Residents and others are being encouraged to avoid the area.

Evacuees from the Aspen Park area waited nervously at nearby Conifer High School, which was packed with those who were displaced, and watched TVs and their mobile devices for news Monday night.

“I don’t know how to feel. I feel blank,” said Sandra Browning, with tears in her eyes.

Browning, who lives off Silver Ranch Road, said she was able to save her birds before she had to evacuate but feared others would not be so lucky.

“My neighbors weren’t home yet, so I am worried about their animals,” she said.

Claire Schmidt, who lives off North Trail Circle, was upset that she was unable to retrieve her dog and cat from her home but even more upset by a frantic message she received from a neighbor.

“She sounded very upset and said something about the fire on her property. I am trying desperately to get ahold of them,” Schmidt said.

The fire was first reported about 2 p.m. Monday. By 5 p.m., it was less than 15 acres. Authorities think it started from embers of a controlled burn done by the Colorado State Forest Service last week.

Smoke from the blaze could be seen from downtown Denver, which only complicated a blowing-dust air-quality advisory issued earlier in the day by the Colorado Department of Public Health and Environment.

The Jefferson County Health Department also warned residents about the possible ill effects of breathing the smoke.

The Federal Emergency Management Agency said Monday night it would approve funds for 75 percent of the state’s eligible firefighting costs.

Monday night, the agency issued a wildfire-smoke health advisory for southern Jefferson, Douglas, western Arapahoe and western Elbert counties because of moderate to heavy drifting smoke.

“With the added particulates because of the smoke from the fires, we could encourage people with heart and lung disease and older residents to avoid prolonged outside activity when the visibility is less than 10 miles,” said spokesman Mark Salley.

Morgan Frost of Elizabeth said she came to Conifer High School to get her mother, who lives off Kuehster Road.

“She is OK,” Frost said. “She is 56 and lives alone. She has 35 alpacas and five dogs. All saved.”

Barbara Webster, a mental-health expert with the American Red Cross, said she had talked to evacuees who were having tremendous difficulty with the situation.

“Some are doing OK and checking on neighbors, but I have spoken to a few who are incredibly upset and scared,” Webster said.

Earlier Monday, crews in Jefferson County fought smaller grass fires near Sawmill Gulch and another off U.S. 40 near Lookout Mountain.

Dry, gusty weather pushed small wildfires across parts of Colorado, including several in the foothills in Jefferson County, as well as fires in Summit, Larimer, Weld and Logan counties.

Joey Bunch: 303-954-1174 or jbunch@denverpost.com