UK firm suggests more shale gas reserves than first thought
3 June 2013 Last updated at 22:55 BST
One of the energy firms hoping to exploit the UK's resources of shale gas says it may be sitting on significantly more gas than previously thought.
UK firm IGas says there may be up to 170 trillion cubic feet (4,810 cubic km) of gas in the areas it is licensed to explore in northern England.
But it remains unclear how much of the gas will be economically extractable.
Shale gas is extracted by fracking - pumping water, chemicals and sand at high pressure into rock to release gas.
John Moylan reports.