The now 550-acre Quarry fire was human caused, Jefferson County sheriff investigator Kevin Bost said Friday.

Investigators are suspicious that the fire started at 9 p.m. on the south side of Deer Creek Canyon, a dark mountain road with no cameras and no streetlights, just west of Grizzly Drive.

“Why would a fire start there at 9 o’clock at night?” asked Jefferson County Sheriff spokesman Mark Techmeyer. “It’s got us scratching our heads.”

“We preliminarily believe that this fire is human-caused in some manner,” Bost said during a press conference Friday morning.

Techmeyer told The Denver Gazette that investigators are unclear whether the fire was caused intentionally or by accident.

Regardless, firefighters are still focused on battling the wildfire, which grew 100 acres on Thursday. 

Two hot shot crews are working with 185 firefighters on the ground with assistance from three helicopters on Jefferson County’s Quarry fire. As of Friday morning, there was 0% containment with dry thunderstorms expected for the afternoon.

The growth was toward open space, though, not spreading toward structures across Deer Creek Canyon Road, one of the most critical areas.

“It’s been a concern from the get-go of this of that fire jumping to the north, which would be our worst nightmare,” Techmeyer said during the press conference about Deer Creek Canyon Road. “We feel very confident where we are with the line along Deer Creek Canyon Road. We do not anticipate that being a problem.”

Karlyn Tilley, a spokesperson for the sheriff’s office, expects positive progress Friday. Concerns regarding potential afternoon storms bringing wind and lightning do exist, though.

Firefighters have built up handlines on the southern and eastern perimeter of the fire, despite tough terrain in the eastern section.

Two hotshot crews are planning to fly the eastern side Friday to find potential ways to attack the fire in that area.

There are around 20 local agencies helping work on the fire, according to Techmeyer, but timeframes are still unclear. 

“As far as what we’re saying to the evacuees about getting in, we wish we could tell them, ‘Today is Friday, we’re going to get you in this weekend.’ But folks, it’s not going to happen,” Techmeyer said. 

“Can we give them a timeframe for next week? We’re hopeful, but we’d be guessing,” he concluded.