Williamsport, Pennsylvania

THE drilling rigs are gone from the hills surrounding this Pennsylvania town of 30,000. The hotels and bars are quieter too, no longer packed with the workers who flocked in their thousands to America's newest and biggest gas field.

The drilling boom of the past seven years is over, even though thousands of existing wells in the Marcellus region still produce a fifth of US natural gas supply. Now, exclusive data made available to Reuters points to a slump in drilling that could hit production next year, defying government and industry expectations of a further rise in output.