Documents seen by BBC News show concerns at the Welsh government and UK Coal Authority that Merthyr Tydfil's Ffos-y-Fran mine may be abandoned
Estimated clean-up costs for the site - the size of 400 football pitches - have grown to between £120m and £175m
Site operator Merthyr (South Wales) Ltd said it was in "constructive dialogue" with Merthyr Tydfil council
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Source and Credit: bbc.com