Fire crews are still on scene putting out hot spots at a converted office building near the Olympic Training Center in Colorado Springs.
Crews have been battling the fire all morning.
A police officer spotted the flames in a building on the 700 block of North Union while driving in the area just after 5 a.m. Wednesday. The building is currently under renovation, and was unoccupied at the time.
Firefighters are restricted to the outside of the structure; they cannot go inside the building because of the damage and the extent of the flames inside. They are using ladder trucks to fight the fire on the exterior.
One firefighter has sustained minor injuries.
KKTV 11 News is told it could be several days before a cause is known.