Kettering, OH – A Kettering man remains in critical condition after an explosion destroyed his apartment.

Sean Quinlan suffered second- and third-degree burns over 35 percent of his body.

Fire investigators returned to the scene of the explosion that happened at 1837 Roslyn Avenue in Kettering on Monday.

Investigators from both Vectren and the Kettering Fire Department spent the day at the scene searching for what caused the destruction.

Late Tuesday, investigators confirmed that the blast was caused by a natural gas leak. There are still trying to figure out where the leak came from, but they said the man who was injured lit a cigarette, sparking the explosion.

Investigators said another man who lived in the complex, Edmund Brown-Edwards, returned to the location on Tuesday. He said he has lived there for 42 and a half years. He returned hoping to salvage some of his belongings.

Brown-Edwards suffered bumps and bruises in the blast. He said he had just stepped outside of his apartment when his front door blew off right on top of him.