Looking again, I think it would have to be an oxy cylinder - they live at Sta 720 - Sta 780 - exactly where the damage is.
However, the presence of luggage would seem to indicate an explosion came within the container unless the bang was big enough to damage and open the sides of the container - but it would have to be a very big bang!
More of a worry, a pax is quoted thus:
"I'm looking at the plane now and on the left hand side, just forward of the wing, there's a gaping hole from the wing to the underbody," she said.
The pic shows damage on the R/H side - unless of course, there are 2 holes......
This might explain:
Peter Gibson from the Civil Aviation Safety Authority says initial reports indicate a problem with the air pressure in the cabin.
"The pilot has some pressurisation warnings about a door on the left hand side of the aircraft, but exactly what went wrong is still being determined," he said.
Could there be 2 different areas of damage?