Box 1-4 sent companies to the 200 block of Hummel Street around 1240 hours for a structure fire. Tower 3 reported they could see smoke from Station 6. Additional calls reported a house in the 1200 block of Kittatinny Street and an explosion had occurred. Units arrived on scene with fire from a vacant dwelling that completely collapsed. Two lines were stretched to knock down the fire quickly. Chief 5 held the box to units on scene with the Squad being committed for an extended period of time. No injuries were reported and the explosion was due to a natural gas leak. Earlier, around 1150 hours, the same box companies responded to the 1200 block of Kittatinny Street for a gas leak. Units investigated, marked control, and turned the incident over UGI. Shortly after the explosion dispatch came in.