Firefighters were called to Empress Road at around 11:50am and are still tackling the huge blaze.
It is believed that fire started in the roof of a building. The road has been closed and ambulance crews are at the scene.
Bevois Valley Road, where you find Jesters and Sobar, has now been closed in both directions between Onslow Road and Thomas Lewis Way.
Kevin Evenett, Incident Commander has said: “We have 79 personnel on scene and ten pumps. We will be here for a while yet damping down, as there are multiple businesses affected.
“It would appear they are all interlinked but fortunately everyone was out when we arrived. It’s definitely a reasonable size incident, and that thick black smoke is tyres, grime and oil.
“Cars were involved in the fire, but we do not know how many. The roof of the building has collapsed in on itself.”
A South Central Ambulance Service has warned people to avoid the area and for locals to keep their windows closed.
The Wessex Scene will keep readers updated as this story develops.