A man has been flown to hospital in Norway after being injured on the Goliat oil platform.
The incident happened on Saturday and the worker is said to be in a serious but stable condition.
A spokesman for Eni said the man is employed by one of the company’s subcontractors and is Norwegian and in his late 40s.
Eni has launched its own investigation, while the Norwegian Petroleum Safety Authority (PSA) said it was also investigating the incident.
Earlier this year, a director at Eni said the Goliat oilfield would still be profitable at $50 oil.
Goliat is expected to peak at around 100,000 barrels a day.
It has been hit with a number of challenges including problems building its FPSO, which has the capacity to store one million barrels of oil.
Goliat has a subsea system comprised of 22 wells and is estimated to hold 180million barrels of oil.
The Italian operator owns a 65% stake in the field with Statoil owning the remaining 35%.