Shell faces pollution inquiry after grounding of rig off Alaska

The US Justice Department is to investigate whether Shell's Kulluk drilling rig off Alaska violated pollution rules.

The Coast Guard has asked federal prosecutors to investigate the grounding of the rig, pictured, on New Year's Eve with a view to possible prosecution. They will look at "potential Marpol violations" – a term relating to marine pollution and used to refer to the International Convention for the Prevention of Pollution From Ships.

Shell Alaska's vice-president Pete Slaiby said: "Our drilling campaigns were completed safely and successfully … It was while leaving the theatre of operations that the Kulluk ran aground."

Shell has suffered a series of setbacks in the Arctic, where it has invested $5bn (£3bn) but has yet to discover commercial quantities of oil. Last week Dave Lawrence, an executive overseeing Arctic exploration, said he was leaving the company "by mutual consent", after 29 years with the company.