[Al Skierkiewicz]

My guess from looking at the failure mode, is that the damage severely bent the strap that tied to the next battery in the pack. When this occured it likely shorted out the first cell in the pack. Fully charged this cell could deliver several amps, enough to heat the strap and the battery and perhaps even welding the strap in place. The other cells in the pack are likely fine and could be used in other applications.