An explosion tore through a residential building near central Istanbul's Taksim Square on Monday, injuring several people.  Television footage showed windows blown out of several multi-storey buildings on the narrow side street. Beyoglu Mayor Ahmet Misbah Demircan said those four people were taken to the hospital. The cause of the blast was not immediately clear, but it was believed to have been caused by a natural gas leak. Governor of Istanbul Huseyin Avni Mutlu said, "The incident occurred most likely following a gas leak or gas cylinder blast."  Firefighters and ambulances have been dispatched to the area.  Police have cordoned off the area and an investigation is underway.