B.C. Ambulance says the explosion happened in the pulverizing room at Teck Resources' Greenhills coal mine near Elkford, about 35 kilometres north of Sparwood.
It says no one was in the room when the explosion happened. The three who were injured were just outside the room, according to B.C. Ambulance.
There's no word yet on what caused the explosion.
History of explosions
This isn't the first time there's been an explosion at the Greenhills coal mine.
Four employees had to be treated for smoke inhalation after a dryer exploded in June 2010. At the time, Teck said the blast caused extensive damage to the building and forced a temporary shutdown of the mine.
The Vancouver-based company is one of Canada's largest publicly traded mining corporations. According to its website, the coal extracted at the Greenhills location is used to make steel.
MAP: Greenhills coal mine in Elkford, B.C.