Colorado officials said on Friday that it was a "miracle" that no deaths were reported in a rare urban fire that moved at breakneck speeds across towns north of Denver, destroying upward of 1,000 homes.
"It's unbelievable, when you look at the devastation, that we don't have a list of a hundred missing persons," Boulder County Sheriff Joe Pelle said. At least seven people had been injured, authorities said, but swift evacuations prevented more casualties.
"And so, again, I'm hoping that's a miracle because it would be, given the circumstances."
Structures were devoured "in just a blink of an eye", said Governor Jared Polis, who lives in Boulder.
The fires erupted on Thursday following an extremely dry autumn and a winter so far nearly devoid of snow. The blaze destroyed about 24.3 square kilometres, Mr Pelle said.
Mr Polis said he had spoken to President Joe Biden, who had verbally approved a major disaster declaration to help people quickly receive financial help following the fire.
Some fires continue to burn but officials are not expecting any growth, he added.
Mr Pelle previously said there could be more injuries — and also deaths — because of the ferocity of the fire, propelled by winds of up to 169 kilometres per hour.
“This is the kind of fire we can’t fight head on,” he said. “We actually had deputy sheriffs and firefighters in areas that had to pull out because they just got overrun.”
The swiftly spreading prairie grass fire is believed to have been ignited by sparks from power lines and transformers toppled by high winds on Colorado's drought-hit Front Range, he added.
Patti Holtz on Thursday described the terror of fleeing her Boulder County home.
“There's embers everywhere. So, it makes me very frightened, of course, with the wind, that it's going to continue to spread to other homes,” she said.
“You just can't see anything. It's like the black of night.”
Evacuation orders were issued on Thursday for all residents in the town of Superior, with a population of about 13,000, and a short time later for the adjacent municipality of Louisville, home to more than 18,000 residents, the Boulder County emergency management office said on Twitter.
Within hours, the blaze had swept through an estimated 650 hectares and destroyed hundreds of homes, Mr Pelle told reporters.
He said 370 homes went up in flames west of Superior and that 210 dwellings were lost in the city's Old Town area, along with other nearby residences. Property losses included a shopping centre and hotel, officials said.
Cooler weather was on its way on Friday and at least temporarily lighter winds had slowed the most destructive bushfire, allowing local authorities to lift evacuation orders outside of Boulder County, The Denver Post reported. Still, tens of thousands of area residents remained under evacuation orders.
Governor Jared Polis said flames had consumed areas the size of football fields in a matter of seconds, calling the conflagration “a force of nature".
A towering plume of smoke from the bushfire was visible in Denver, about 32 kilometres to the south.
Gusts of up to 177 kilometres an hour were reported in Boulder, the National Weather Service reported.
Wind speeds were forecast to drop on Friday, which would enable firefighters to get ahead of the flames and for water-dropping helicopters and aircraft tankers to be deployed, authorities said.
The fire on the outskirts of the Denver metropolitan area, left bone dry from an extreme drought gripping eastern Colorado, follows several days of heavy snow in the Rocky Mountains to the west.
Snow is forecast for Denver and eastern Colorado on Friday.
Agencies contributed to this report