DENVER (CBS4)- Investigators are trying to determine what caused a fire that destroyed a commercial building late Thursday night.

Firefighters rushed to what appears to be an old Habitat for Humanity Building after they received a call from RTD at about 11 p.m. Thursday.

Dozens of firefighters worked to get the fire under control so they could extinguish it.

Firefighters said smoke was smoldering for a while before the fire really started burning inside the building at 12th and Pecos.

Firefighters were able to get inside the building to make sure it didn’t spread to others next door.

“It was starting to go through the roof, they kept the fire from spreading, they did a great job. They were able to knock it in from the interior. They knocked it down rather quickly in heavy heat conditions and zero visibility. High, high heat conditions,” said Denver Fire Department Lt. Phil Champagne.

No one was inside the building and there were no injuries reported.

Fire investigators are hoping they will have more information into how the fire started by Friday afternoon.