A rapid-response team from the National Transportation Safety Board and officials from CenterPoint Energy are investigating an explosion possibly linked to natural gas at the Minnehaha Academy in Minneapolis. The explosion at mid-morning Wednesday killed two people and injured several others. The bodies of school receptionist Ruth Berg, 47, and part-time custodian John F. Carlson, 82, were recovered. According to initial reports, the explosion and fire led to the partial collapse of an upper school building. At least nine people were taken to the Hennepin County Medical Center.