Two pumping appliances from the town and a water carrier from Ventnor are currently on the scene tackling the blaze, which has taken hold of old hay stored in an open-sided barn.
Firefighters wearing breathing apparatus are continuing to dowse the flames. They were called to the scene shortly before 16:50.
Due to the unsafe roofing, firefighters are unable to enter the barn to distribute the hay and are therefore letting it burn in a controlled manner until they are able to drench and extinguish the remainder.
No persons or animals have been involved in the incident.
The road remains open in both directions, with light smoke blowing across the carriageway.
UPDATED @ 18:12 – The fire has been extinguished however fire crews remain on scene damping down the area.
Two appliances and an officer were mobilised to the scene at around 11:00, however one pumping appliance has since returned to station.
Firefighters are damping down the area using a hose reel.