Kentucky ? The sole survivor of a mine explosion in southeastern Kentucky said Friday that he doesn’t know how long his air pack lasted after the blast that killed five fellow miners.

Whether better oxygen masks could have saved lives in the May 20 explosion haunts the victims’ families and has been part of the investigations.

Paul Ledford stood outside to show his support for the grieving families as federal officials started their closed-door interviews.

Three of his fellow workers died of carbon monoxide poisoning, while two more died from injuries in the blast at Kentucky Darby Mine No. 1.