(CNN) -- A day after a wildfire forced the evacuation of 223 houses near Boulder, Colorado, residents of the fire-damaged Lefthand Canyon area began returning to their homes Saturday.
Public safety officials announced Saturday afternoon that the blaze was "60% contained," and that firefighters had prevented a dozen homes from being damaged or destroyed. However, officials cautioned that residents in the threatened area should remain vigilant in case the fire is revived.
"We ask that people remain attentive, because if we have a change in the weather conditions -- the wind picks up, the fires start running -- there is a chance we'll have to do another mandatory evacuation," Boulder County Sheriff's Cmdr. Rick Brough told reporters at a press conference. "So what we ask is they continue to watch the news and stay near the phone."
Brough said the county has a "reverse 911" system that allows his department to notify area residents if necessary.
The fire broke out 6:45 a.m. ET Friday near Longmont Dam Road, north of Button Rock Reservoir in Boulder County, according to emergency management officials. By mid-morning, 50 firefighters from at least a dozen departments were on hand amid burning brush and billowing smoke, and 223 homes had to be evacuated.
U.S. Forest Service spokeswoman Maribeth Pecotte told reporters that changing weather conditions forecast Saturday were expected to make it easier to put out the fire. Humidity was rising, temperatures were falling and rain and snow were expected to fall on Lefthand Canyon Saturday night, she said.
The cause of the fire remains under investigation, Pecotte said. The blaze, she said, started in a heavily used recreational area on national parkland.
"We're not sure what kind of human cause (is responsible for the fire)," Pecotte said. "The investigation is ongoing and they're going to figure that out."