This is what could happen if a Li-Ion battery pack on a notebook PC malfunctions. This is somewhat scary.
From: the pcpitstop.com article
We intentionally created conditions in which the Li-ON[sic] battery pack would explode inside a generic portable. The results are dramatic. There are numerous conditions where these fires can occur in real life. Faulty battery packs (driving the recalls), faulty protection circuits inside the PC, exposure to excessive heat, and blunt force are some of the major ways that this could happen to you.