As many as 50 residents have been forced from their homes by a fire that broke out early Friday at the Gold Run Condominium complex in Boulder.
The fire erupted about 2:45 a.m. in one section of the three-building complex, located east of the University of Colorado campus.
Officials say it was contained by 7 a.m.
Dozens of crews from Boulder, Longmont, Louisville and Mountain View responded to the blaze.
Boulder police spokeswoman Julie Brooks says the cause isn't known but arson investigators are on the scene.
The American Red Cross is assisting the affected residents.
Authorities say at least three people have been taken to a hospital for smoke-related injuries.