If there is an air bubble inside a wooden log, and the log gets on fire, would that air bubble make the log explode or snap?

It’s buggin’ me a bit now. Why do wooden logs explode when on fire sometimes? I was wondering that, and then I came up with a theory that there are air bubbles inside that…uh…create pressure or something that causes mini explosion.

Is that possible? If you have an air bubble in a wooden log, and the log gets on fire, could the heat make some pressure in the bubble and cause the log to explode (or simply snap real loud)?
How big would the bubble have to be? How high the pressure?

Can there even be an air bubble inside a wooden log?