A propane gas explosion is believed to be the cause of a fire that severely damaged a condemned house and seriously injured one person early Monday morning, officials said. The Bangor Fire Department and Bangor Police Department responded to the blaze at 75 4th St.

A preliminary investigation found that the blaze at the house, which had been condemned, was likely started by a propane explosion.

Officials say the fire happened at a condemned single-family home that had been boarded up by the city, and a witness reported seeing someone jump from the house.