Fire investigators are looking into what caused a house explosion in West Baltimore late Thursday. Firefighters were called to North Monroe Street in the Sandtown-Winchester neighborhood just before 11 p.m. The house that exploded was vacant and located in the middle of a group of row homes. The fire from the first house damaged an occupied house next door. According to Baltimore City Fire officials, a natural gas explosion is most likely the cause of the explosion. The fire still remains under investigation, and no official cause has been given. No injuries have been reported at this time.