The oil giant has confirmed that a blaze was detected in a store room on the vessel, around 120 miles west of Shetland, on Saturday afternoon.
Coastguard helicopters were called and 30 non-essential workers were evacuated to nearby installations.
Five people had to be assesed for smoke inhalation but required no further treatment.
The blaze was subsequently extinguished and poses “no further risk to personnel, the environment or the asset”, said Altera, the duty-holder for the vessel.
A spokeswoman for HM Coastguard said on Saturday: “HM Coastguard received a call from an offshore installation reporting a fire on board just after 3pm on April 2.
“The installation is approximately 95 nautical miles west, north-west of Sumburgh, Shetland.
“Coastguard helicopters from Sumburgh and Stornoway have been sent to evacuate a number of the crew to nearby installations.
“A coastguard fixed wing aircraft is also due on scene to provide safety cover for the helicopters. On board firefighters are responding.”
Production from the Foinaven area was suspended last year after it was announced that the vessel, which started up in 1997, is to be retired – work has been ongoing to prepare it for removal.
BP handed in the decommissioning plan for the FPSO earlier this year after a string of HSE issues cropped up.
Altera, which is currently chartered by the London-listed company, will resume control of the vessel following removal from the field.
It was recently reported that BP is hoping to sell its 100% interest in the Foinaven area, with hopes that a current drive for energy security could attract buyers.
A BP spokesman said: “BP is working with Foinaven Petrojarl FPSO duty holder Altera Infrastructure after a fire was detected in a store room on board the vessel on Saturday [2 April].
“The incident was brought under control and, as a precaution, 30 non-essential personnel were safely transferred to nearby installations.
“Five people were assessed for possible smoke inhalation but no further treatment was required.
“The safety of our staff and contractors is central to everything we do and we will continue to work with Altera Infrastructure and the relevant authorities to understand what happened on this occasion.”
An Altera spokeswoman said: “We can confirm that the Petrojarl Foinaven was involved in an incident on April 2nd at the Foinaven field, 190km west of the Shetland Islands.
“A fire was detected in a store room, which was controlled and extinguished. Five people were assessed for possible smoke inhalation and required no further treatment. 30 non-essential personnel were immediately transported to nearby assets as a precautionary measure.
“Relevant authorities have been notified in accordance with standard procedures. The incident poses no further risk to personnel, the environment or the asset.
“Safety is Altera Infrastructure’s first priority in all operations. We have initiated an investigation to understand the circumstances around this incident in order to prevent reoccurrence.”