 Additionally, he persuaded George Mueller, head of NASA's Office of Manned Space Flight, to allow him to act as Mueller's deputy in Florida, supervising the progress of the investigation.Named to the advisory group chosen to support the review board, Shea threw himself into the investigation, working eighty-hour weeks.Although the precise source of ignition was never found, it soon became clear that an electrical short somewhere in the command module had started the fire, probably sparked by a chafed wire.