The National Transportation Safety Board said Friday that the work was being done Wednesday at Minnehaha Academy as part of gas company CenterPoint Energy's plan to move meters from inside buildings to outside for easier access. NTSB board member Christopher Hart says investigators want to know as much as they can about the contractor, Master Mechanical, and the oversight conducted during the "hazardous operation." The local medical examiner says the two people who were killed during an explosion at a Minneapolis school died from blunt force injuries sustained when part of a building collapsed. Berg and Carlson were longtime employees of Minnehaha Academy, a private Christian school with about 800 elementary and high school students. The private school in Minneapolis where an explosion and partial building collapse killed two people and injured nine others is planning a memorial service for the school custodian who died in the blast. A team from the National Transportation Safety Board is on scene to determine what caused the natural gas explosion. Administrators at a private Minneapolis school where an explosion and partial building collapse killed two people say the start of classes for some students will be delayed about two weeks. A team from the National Transportation Safety Board arrived in Minneapolis Thursday to begin the painstaking task of determining what caused the natural gas explosion, which killed two school workers.