Fire fighters are tackling a blaze which has broken out at the Fair Isle Bird Observatory.
Reports of the fire were received at around midday, said the Scottish Fire and Rescue Service.
A crew from the island were first on the scene and they were later joined by a crew from Lerwick, who were flown to Fair Isle by Coastguard helicopter.
A second crew from Lerwick and one from Sandwick are also set to attend the scene.
Two main jets, two hose reel jets and two sets of breathing apparatus have been used. No injuries have been reported.
As of 3.30pm the incident remained ongoing, said fire control.