PaperTiger-
Thank you for the clarification-and for posting the link to the Metro incident.
My suggestion though, was not that a hydraulic or landing gear issue caused this, but simply that heat from a fire could cause a structural failure of the wing. From the TSB report on the Metro incident-"The initial event in the break-up sequence was the failure of the front wing spar, caused by intense heat." Of course a fire may ignite due to an unkown number of circumstances, but an engine nacelle is one of the more susceptible locations for obvious reasons. I really need to stop speculating though....I think I'll bow out till the NTSB has had a chance to do their job.