Oil and gas operator EnQuest is understood to have multiple suspected coronavirus cases on board a Northern North Sea platform.
A source told Energy Voice that around eight crew have been self-isolated on the Magnus platform.
The Magnus field lies 99 miles north east of Shetland.
All affected and quarantined workers are thought to be travelling onshore by helicopter later today.
EnQuest refused to comment on specific cases or confirm the number of suspected cases on the Magnus platform.
A spokeswoman for EnQuest said: “As a responsible operator, the safety of our people at EnQuest is our first priority.
“We have been working with a variety of stakeholders, including industry and medical organisations, to ensure our operational response and advice to our workforce is appropriate and commensurate with the prevailing expert advice and level of risk.
“We have implemented a number of actions offshore and onshore to keep our people safe and maintain safe operations.
“For any individuals that present with symptoms offshore, we have isolation and treatment plans in place and, along with other operators in the North Sea, have access to a dedicated helicopter service used only to transport those with suspected coronavirus back onshore.”
Last week, EnQuest struck a deal with fellow operators Total, Shell, CNR, Taqa, Spirit Energy and Equinor to fund a new ‘Corona copter’ to bring confirmed and suspected Covid-19 sufferers back to shore.
CHC Helicopter will began providing the new, dedicated service last week.
Yesterday, Taqa confirmed that 13 cases of suspected Covid-19 had been identified on its North Cormorant and Cormorant Alpha platforms in the North Sea.
Eight of those workers have returned onshore.