Colorado fire: 2 people missing as officials probe cause of inferno

Two people are still missing after initial hopes that no one was killed in last week's blaze

Two people remain missing after a massive fire raged through a suburban area near Denver, Colorado last week. One other person who had earlier been reported missing has been accounted for, authorities said on Monday.

Investigators were still trying to determine what caused the flames to tear through at least 24 square kilometres, leaving nearly 1,000 homes and other buildings torched.

Boulder County Sheriff Joe Pelle on Saturday said authorities were pursuing a number of tips and had executed a search warrant at “one particular location.” He declined to give details.

“It’s complicated and it’s all covered with a foot of snow,” Mr Pelle said of the scene where the fire started.

“The outcome of that investigation is vital — there is so much at stake. We are going to be professional. We are going to be careful.”

Mr Pelle said officials were aware of a viral video showing a shed on fire in the area where the blaze originated, but noted they do not yet know if the shed was the start of the fire or "secondary", according to CNN.

Utility officials found no downed power lines around where the fire broke out in the area located between Denver and Boulder. The wildfire came unusually late in the year, following an extremely dry autumn and amid a winter nearly devoid of snow, conditions experts say certainly helped the fire spread.

At least 991 homes and other buildings were destroyed, Mr Pelle said: 553 in Louisville, 332 in Superior and 106 in unincorporated parts of the county. Hundreds more were damaged. He cautioned that the tally from the wind-whipped wildfire is not final.

The totals include destroyed barns, outbuildings and other structures, but the vast majority were homes, Boulder County spokesperson Jennifer Churchill said late on Saturday.

Authorities had said earlier no one was missing. But Ms Churchill said that was due to confusion inherent when agencies are scrambling to manage an emergency.

Mr Pelle said officials were organising cadaver teams to search for the missing in the Superior area and in unincorporated Boulder County. The task is complicated by debris from destroyed structures, covered by 20 centimetres of snow dumped by a storm overnight, he said.

At least seven people were injured in the wildfire that erupted in and around Louisville and Superior, the neighbouring towns about 32 kilometres northwest of Denver with a combined population of 34,000.

The blaze, which burned at least 24 square kilometres, was no longer considered an immediate threat — especially with the overnight dumping of snow and frigid temperatures on Saturday.

The snow and low temperatures cast an eerie scene amid still-smouldering remains of homes. Despite the shocking change in weather, the smell of smoke still permeated empty streets blocked off by National Guard troops in Humvees.

The conditions compounded the misery of residents who started off the new year trying to salvage what remained of their homes.

Utility crews struggled to restore electricity and gas service to homes that survived, and dozens of people lined up to get donated space heaters, bottled water and blankets at Red Cross shelters. Xcel Energy urged other residents to use fireplaces and wood stoves to stay warm and keep their pipes at home from freezing.

Families filled a long line of cars waiting to pick up space heaters and bottled water at a Salvation Army distribution centre at the YMCA in Lafayette, just north of Superior.

Monarch High School seniors Noah Sarasin and his twin brother Gavin had been volunteering at that location for two days, directing traffic and distributing donations.

“We have a house, no heat but we still have a house,” Noah Sarasin said. “I just want to make sure that everyone else has heat on this very cold day.”

The Associated Press contributed to this report