Thunderstorms Wednesday afternoon made things more difficult for firefighters still working to contain the 407-acre Treasure Fire that broke out near Leadville Saturday.

No structures have been damaged or threatened by the fire, and no evacuations have been ordered.

The blaze, located roughly 10 miles southwest of Quandary Peak, is now 25 percent contained, but teams were called off the fight for as long as an hour Wednesday due to lightning, officials said.

Increased humidity created problems with back fires and concerns with new starts while rain also made it difficult to start the controlled burns being used to stifle the Treasure blaze by eliminating its fuels.

Still, the fire has not grown since Saturday evening.

“It’s in a vegetation site that tends to burn in a spectacular crown fire or barely creep at all (on the ground),” fire spokeswoman Sarah Gallup said. “Between suppression efforts and the weather we haven’t had any crown-ons.”

The approximately 100-acre increase in size from Sunday is due to intentional burning taking place between the flames and fire lines.

The containment effort hasn’t been easy, Gallup said. The entire fire is situated above 10,000 feet and in some locations surpasses 12,000 feet, making work difficult for firefighters, many of whom are from sea level, carrying heavy gear.

The accumulation of pine needles and debris under spruce trees in the fire’s path is also making the work of digging out fire lines time consuming.

The crew fighting the fire has grown to 123 people.

Authorities still don’t know what started the fire, but they have ruled out lightning. Officials said earlier this week they believed the blaze was human-triggered, but it is still under investigation.

The Treasure Fire broke out at roughly 11 a.m. Saturday morning, when fire danger in the area was rated to be extreme and much of western Colorado was under a red flag warning.

It is burning 5 miles northeast of Leadville in Birdseye Gulch on the western side of Mosquito Peak.