Fire investigators have finished their on-scene investigation of the fire that destroyed KREX-TV on Sunday.

According to Mike Page with the Grand Junction Fire Department, the cause of the fire will be classified as undetermined. Investigators will follow-up with evidence that was sent to a lab, as well as conduct more interviews to see if they can determine the exact cause, however, Page says they may never be able to determine what exactly started the fire. That is because of the large size of the fire and the large amount of destruction it caused.

Investigators did pinpoint the origin of the fire. They say it started in a hallway next to an office in the north and center part of the building. They say based on what they have found so far, they do believe the fire was started accidentally.

The Grand Junction Fire Department says it had to pull firefighters from the building shortly after they arrived on scene. They say because of the building's many remodels and the rapidly growing fire, it wasn't safe for firefighters. The 22 firefighters then pulled back, and focused on trying to extinguish the blaze from outside the building. Shortly after the crews left the building, two separate smoke explosions spread the fire to the entire building.

The building didn't have a fire sprinkler system, and apparently no working smoke detectors. The fire department says the four or five people who were in the building at the time of the fire were notified by bystanders. They were able to leave the television station without injury.