A crewman was airlifted to hospital after he was injured aboard an offshore platform.
The accident happened on Statoil's Mariner A platform in the Mariner field, 93 miles east of Shetland, at about 17:00 on Monday.
Coastguards sent a helicopter to pick him up from Prosafe's Safe Boreas accommodation platform.
The man was taken to Lerwick's Gilbert Bain hospital. Statoil said he was later released.
A Statoil spokesperson said: "An incident involving an individual who sustained an injury whilst working on the Mariner A installation was reported yesterday evening.
"The individual was taken shortly afterwards by Coastguard helicopter to Shetland for medical treatment and has since been released. The family of the person involved has been informed.
"Our first priority is to ensure the safety of our people. An investigation is under way to analyse the cause of the incident and determine any remedial actions."