Well, it looks like the swelling is due to gas..... hydrogen, carbon monoxide, carbon dioxide and others..... which are helpfully described as "toxic".
Given that lithium itself reacts violently when it comes into contact with water and gives off hydrogen in an exothermic reaction, it's not surprising that fires have been reported.
The cell seems really, really solid, so the idea that it is swollen due to gas seems odd.... I can't imagine that the envelope would sustain the kind of pressure necessary...... but It's certainly not staying on my desk!