TALLMANSVILLE, W.Va. - As the victims' families made plans for the first of the funerals, officials worked Friday to purge the Sago Mine of poisonous gases and allow investigators to determine what sparked the blast and how the miners spent their final hours.

Workers began drilling three ventilation holes into the mine. But International Coal Group chief executive Ben Hatfield said it could be days before the first investigators go in.

“There are so many things we don't know about what went wrong,” Hatfield said. “We don't want to put any more people at risk until we know answers.”

The Mine Safety and Health Administration appointed an eight-person team to investigate Monday's blast that killed one miner immediately and left 12 others trapped more than two miles inside. The team will examine every aspect of the mine, including its physical structures and all equipment. They will be looking for the direction of the explosive forces. They will take dust samples. They will seize any equipment that might have contributed to the blast and, if necessary, test it in a lab.

The investigation will also involve interviews with dozens of people, including the approximately 13 miners who escaped, workers on previous shifts, and managers, Friend said. The sole survivor's recollections also could prove crucial.