At least six people were killed and more than 50 others injured following a massive explosion on the ground floor of a three-storey building in Dhaka's Moghbazar area, Bangladesh police has confirmed.A five-member probe committee of the Fire Service and Civil Defence has launched an investigation into the explosion on Sunday evening and asked to submit a report within three days, a top official told IANS here.Officials of the Fire Service and Civil Defence suspect that two LPG gas cylinders might have exploded at the Shawarma House located on the ground floor of the building."The explosion might have occurred in te Shawarma House on the ground floor of the three-storey building... That's our primary suspicion," Sajjad Hossain, the Director General (DG) of Fire Service and Civil Defense, told IANS.Meanwhile, Samantalal Sen, head of the Sheikh Hasina National Institute of Burn and Plastic Surgery of Dhaka Medical College and Hospital, told IANS of the five severely burnt injured victims, three were currently in a coma.Only three of the casualties have been identified so far as Jannat Aktar, 23, her nine-month-old daughter Subhana, and Md Swapan, 35.According to witnesses, a thick column of smoke engulfed the area soon after the explosion at around 7.35 p.m.Mahsuma Safta, a witness, told IANS that as a result of the blast, a portion of the building immediately collapsed, while glasses of three buses parked on the nearby road and the window panes of an adjacent building were shattered.At least 15 fire tenders rushed to the spot to douse the flames, while a search and rescue operation is underway to look for more trapped persons under the debris.