The pair who were inside managed to leave the flat and were detained by police at the scene.
Both men who are in their 30s were taken to Dudley's Russells Hall Hospital after suffering nine per cent burns to their hands and lower backs. They will be questioned about what happened when they are fit to do so.
No one else is believed to have been injured in the explosion or fire, but structural damage was caused to the house, leading to the evacuation of 20 residents from homes in the immediate vicinity as a precaution.
As investigations continued today, a bomb disposal unit attended the address in Oldbury Road after concerns were raised that military collectable items were in the flat next door. Entry was forced under section 17 to protect life and property, but the items were declared safe.
The 20 people spent last night in temporary accommodation following the explosion just before 10.05pm.
The fire was put out within an hour.
Jamie Arrowsmith, a West Midlands Ambulance Service spokesman, said: "On arrival, crews found a semi-detached property ablaze. The property is split into four flats.
"Crews were told the fire started following an explosion in one of the flats.
"There were two patients, both men in their 30s who were already out of the property prior to our arrival.
"They had both suffered 9% burns to their hands and lower back. They were assessed and treated on scene before being transported to Russells Hall hospital."
Fire crews also attended the blaze.
Oldbury Road has now reopened.
Anyone with any information about what happened is asked to contact police on 101.