Three people have suffered serious burns to their heads and faces after an explosion at a southeast Calgary welding shop that was powerful enough to blow the doors off the building, officials say.

The blast took place at Hennessey Welding, in the 11000 block of 114th Avenue S.E. at around 1:15 p.m.

Three men sustained burns when a propane tank exploded while some work was being done on it, said Calgary Fire Department spokeswoman Carol Henke.

There was no structural damage to the building, but the doors and windows were blown out and the metal siding was bent outward.

"The doors were blown quite a substantial distance from the building due to the force of the explosion," said Henke.

Paramedics treated three men between the ages of 30 to 55, all suffering from serious burns to their heads, faces, and necks as a result of the explosion, according to EMS spokesman Adam Loria.

All three men were transported to Foothills Medical Centre in stable, non life-threatening condition.

Occupational health and safety officials are investigating.

Police tape now going up around scene Hennesy Welding in the SE. 3 patients taken in ambulance <a href="https://twitter.com/hashtag/yyc?src=hash">#yyc</a> <a href="https://t.co/S6VVEFp3Kd">pic.twitter.com/S6VVEFp3Kd</a> —@StephWiebeCBC

On scene of a propane explosion in Calgary SE. EMS + Fire here too. <a href="https://twitter.com/hashtag/CBC?src=hash">#CBC</a> <a href="https://t.co/arxksawTAe">pic.twitter.com/arxksawTAe</a> —@StephWiebeCBC