We know that the lithium-ion battery experienced a thermal runaway, we know that there were short circuits, and we know that there was a fire. The work that we continue to do will tell us why these things happened.
...And it is answering the "why" question that will ensure that the appropriate corrective actions are taken," she said while briefing the results of NTSB investigation.
Investigation into Boeing 787 Dreamliner battery shows short circuiting - The Times of India