Gardaí and the Health & Safety Authority are investigating the death of a man at the Corrib gas tunnel in Aughoose, Co Mayo.
The 26-year-old German man sustained head injuries while working as part of a maintenance support crew just before 9am on Sunday.
The man was pronounced dead at the scene.
His body was taken to Mayo General Hospital for a post mortem examination.
The Wayss & Freytag BAM Civil Joint Venture, which runs the operation, said the man was working for subcontractors Herrenknecht.
The group said all operations have been suspended at the site as the investigations are carried out.
It has offered its condolences to the dead man's family.
Shell E&P Ireland has also expressed its condolences to his family and co-workers.