It's not alleged -- it's real. You are thinking of Centralia, Pennsylvania, where an underground coal seam has been burning since 1961 (or 1962, depending on the source). See:
10 posted on 06/14/2008 7:16:59 PM PDT by NewJerseyJoe
(Rat mantra: "Facts are meaningless! You can use facts to prove anything that's even remotely true!")