The exact composition of chemicals used in fracking is not always released by fracking operators, but is believed to vary from site to site.
The majority of the fracking mixture which is pumped into underground shale rock to force gas out is water and sand, but other chemicals are included. These have ranged from hydrochloric acid to citric acid, and are one of the reasons fracking is opposed by campaigners.
What constitutes an offence of corporate manslaughter? Who can be prosecuted for it and what are the punishments?