COLORADO SPRINGS, Colo. (CBS4) – Firefighters in Colorado Springs believe a space heater caused an explosion that sent two people to Denver hospitals.

The garage at a home on Greenwood Circle exploded on Sunday. A 2-year-old boy was listed in critical condition at Children’s Hospital. His father is also in critical condition at a Denver hospital.

Firefighters say the man was a mechanic and was using a propane space heater while he worked on a vehicle. When the garage door closed, the fumes ingited.

Another man was also injured.