The factual findings are here. 48 PDF pages. The NTSB preamble to the Interim Report:
The National Transportation Safety Board (NTSB) notes that the information discussed in this interim factual report is based on initial findings from the investigation of this incident. Because the investigation is continuing , no conclusions or recommendations are being made at this time. Readers are encouraged to access the public docket for this incident (DCA13IA037) for further details about the information presented in this report.
In addition, readers are advised that the information presented in this report could change if new evidence becomes available.
The Seattle Times reports the NTSB plans public hearings on lithium-ion battery safety.
Reuters reports that the NTSB has not found the root cause of the Japan Air Lines incident.