Separating long-term glued 'Conti' board

I'm trying to separate some 'Conti' type chipboard that has been glued together for a long time (years). The pieces were about 1'x2' glued and screwed onto a side of a cupboard (also Conti type board). I've removed the screws and tried prising it apart. I've got some off, other bits have split leaving bare chipboard of the smaller bits. Ideally I'd like to get it all of leaving a 'perfect' surface behind (well, reasonably nice - like keep the coating on the side of the cupboard that is staying!)
So - any hints as to remove the split chipboard? Would getting it wet help get it off? I've not idea what sort of glue was used.

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