Natural causes 'all but ruled out' in Colorado wildfire

(CNN) -- With firefighters close to extinguishing one of the most destructive fires in Colorado's history, investigators have "all but ruled out natural causes" in the blaze near Colorado Springs, a sheriff told reporters Thursday.

Authorities still are determining what caused this month's 16,000-acre Black Forest Fire, which killed two people, destroyed more than 500 structures and prompted tens of thousands of people to flee.

But investigators scouring a 24-square-foot area where the fire is thought to have started believe a natural cause is out of the question, El Paso County Sheriff Terry Maketa said.

"I can't really go any further on that, but I can say we are pretty confident it was not, for instance, a lightning strike," he said.

Maketa said earlier this week that the fire was being treated as a crime scene, meaning in part that investigators were preserving every piece of evidence that they could. But he said he wasn't ready to say whether a crime was committed.

The fire was 95% contained Thursday morning, and firefighters planned to have it contained fully by Thursday evening, federal incident commander Rich Harvey said.

The blaze rapidly ravaged woods and neighborhoods in a mostly rural area northeast of Colorado Springs last week, and firefighters struggled to keep up in the early days, thanks to little rain and blustery winds. But more favorable conditions helped firefighters raise containment from 5% Friday to 65% Sunday.

County spokesman Dave Rose told CNN last week that the fire appeared to be the most destructive in the history of Colorado.