Two people were still missing and feared dead after a wildfire roared through two towns in Boulder County, Colorado, and destroyed nearly 1,000 homes, authorities said on Sunday.
Boulder County Sheriff Joe Pelle said at a press briefing on Sunday that one person who had been reported as missing on Saturday was accounted for and was not harmed.
Pelle said the two missing people, whom he did not identify, lived in homes that were consumed by the blaze.
Search teams using dogs trained in finding bodies were working in rough conditions on Sunday, trying to find any human remains that may be among the burned buildings, Pelle said.
Officials initially said there were no reports of fatalities following the rare urban wildfire that erupted on Thursday afternoon on the northern outskirts of the Denver metropolitan area.
Pelle has declined to provide many details about the investigation into how the fire started. However, he did say that investigators have determined the fire started near the intersection of a state highway and another road in south Boulder.
The intersection is near where a video posted on Twitter showed a shed on fire Thursday before the wider wildfire began.
"We don't know that that shed, or anything around it, was the actual start of the fire, or whether it was secondary," Pelle said. "It's complicated and it's all covered with a foot of snow today."
Wind gusts on Thursday in excess of 100 miles per hour (160 km per hour) pushed flames eastward into the towns of Superior and Louisville, prompting the evacuation of both communities.
In about two hours, the fire had scorched over 6,000 acres, officials said, with the fire at times moving a football field length in seconds.
Pelle said 991 homes in Superior, Louisville and in unincorporated parts of the county have been destroyed, making it the most destructive wildfire in state history in terms of residences lost.
Officials initially said sparks from downed power lines that were toppled by the gale-force winds may have sparked the blaze, but an inspection by utility company Xcel Energy found no damaged or downed lines near the fire's believed origin.
U.S. President Joe Biden has declared the scene a national disaster, freeing up federal funds to assist affected people and businesses in recovery efforts.
Governor Jared Polis said Sunday, "I know this is a difficult time in your lives ... We will build back stronger because we are Colorado strong."