Semi-submersible drilling facility Scarabeo 8, owned by a division of Spanish contractor Saipem and leased by Italian energy company Eni for the Barents Sea, reported a 5.7-degree list Sept. 4.
The Norwegian Petroleum Safety Authority announced it was investigating the incident, which the PSA said occurred because of the unintentional filling of a ballast tank.
"The incident triggered an alarm and mustering of personnel," the agency said. "There were 140 people on board when the incident occurred."
The PSA said a preliminary investigation found the incident occurred because of incorrect operations at the rig. Eni and rig owner Saipem have been under close observation, the agency added.
None of the companies involved offered a public comment. PSA said the incident cause no major problems but was considered serious enough for an investigation.
"The investigation will focus on Saipem's management of capacity and competence," the agency stated.