Authorities in Colorado searched for answers Monday as they investigated what caused the fire that torched scores of homes and displaced residents in the suburbs of Denver last week.
At least two people were still missing and more than 1,000 houses and businesses were destroyed or damaged in the fire that blitzed a 10-square-mile area in Boulder County around the towns of Superior and Louisville.
Authorities initially said downed power lines may have caused the fire, which started Thursday, but Boulder County Sheriff Joe Pelle said Monday there's an "open and active investigation" into the origin of the flames — a probe that could take weeks or months.
Pelle said it's important the investigation is done right and "that is more important than the urge for speed that a lot of folks are feeling right now."
Though Pelle provided few details about the investigation, he said one neighborhood west of the towns was at the center of the inquiry.
"I'm not a trained fire investigator. It’s really obvious where that fire started and what direction it went in,” Pelle said.
Authorities completed a search warrant at a home in the area, and Pelle said they received a number of tips. He also acknowledged a video that appeared to show a shed burning nearby but said it was unknown whether that shed was the start of the fire or a secondary fire.
"It's complicated, and it's all covered with a foot of snow," he said.
'Rebuild, recover, heal': 2 still missing, hundreds of homes gone after Colorado wildfire
It snowed Friday, which helped firefighters get the flames under control. But the snow has complicated the search for the two missing people and the investigation into the fire's origin, Pelle said. Hot debris from the fire also remains in some areas.
Pelle said Saturday that downed power lines had not been found in the area where the fire is believed to have started. Downed telecommunication lines, however, have been found.
Pelle also said people shouldn't have lighted fires the day flames broke out given the windy conditions. "If it turns out to be arson or reckless behavior with fire, we’ll take appropriate actions," he said.
At a news conference Sunday, Colorado Gov. Jared Polis said: "If there was any form of deliberate or accidental arson, I fully expect that any of those responsible will be held fully responsible under the law for the utter devastation that was caused."
On the day the fire started, the area was experiencing unusually high winds after months of dry weather. Forecasters at the National Weather Service have said the combination of more than 100 mph winds and record dryness in the region likely helped fan the flames.
After the fire sparked, families had in some cases only minutes to evacuate the area. "Just in the blink of an eye. This was a disaster in fast motion, all over the course of half a day," Polis said Friday.
Authorities were still searching for two missing people Monday, with crews scavenging two separate buildings where the individuals were believed to have been before the blaze. Both structures were destroyed in the fire and blanketed in the aftermath with several feet of snow.
Pelle said crews were searching both buildings by hand, working with small tools to get through the locations.
'It couldn't be saved': Snow helps quell Colorado wildfires as evacuees face devastation
Pelle said federal partners were helping with the investigation.
"There's so much at stake, and so we're going to be careful. We're going to be professional. We're going to bring in the best people in the country. We're going to do this right, and we're not going to rush."
Contributing: John Bacon and Celina Tebor
This article originally appeared on USA TODAY: Colorado fire origin: Investigators seek cause of Boulder wildfire