Could fracking contaminate UK water supplies?
The potential of fracking to contaminate drinking water with methane in the UK has been assessed in a new report.
A map of where key aquifers in England and Wales coincide with locations of shale has been produced by the British Geological Survey and the Environment Agency.
The risk of methane being released into drinking water has long been one of the most sensitive questions over fracking.
The BBC's science editor David Shukman explains the report's findings.