Just before 5:30 p.m. MT, people in the Alberta mountain town reported a large boom and a plume of smoke.
A town official says the explosion happened next to a construction site by a seniors' home at Fairholme Drive and 13th Street.
People should avoid the area, said town spokeswoman Sally Caudill, who added that initial reports suggest a house had exploded.
Crews are evacuating people from the area and putting out spot fires, officials indicated on the town's website.
It's not yet known what caused the explosion.
Calgary EMS spokesman Adam Loria said one person was transported to hospital in stable condition with minor injuries.