It was four months ago today that an explosion led to the deaths of a dozen miners inside the Sago mine in West Virginia.
Two days of joint state-federal hearings into the January disaster begin today, with victims' family members among those testifying. Governor Joe Manchin, state and federal officials and mine company representatives will also speak.
Investigators still haven't determined just what led to the blast, even though the mine's owner has said it thinks a lightning strike somehow triggered it.
Relatives have said they want to know why it took federal officials eleven hours after the blast to let rescue crews inside the mine.
Some of the hearing will focus on the contents of a letter sole survivor Randal McCloy wrote to his colleagues' relatives, including his statement that some air packs the miners carried failed after the explosion.