The fire started in a property in Haviland Road, Ferndown. Shortly after Dorset Fire crews arrived they requested more for help. Aappliances from Ferndown, Wimborne, Redhill and Poole were mobilised and eight crews were sent to the scene.
Additional crews from Westbourne, Springbourne, Verwood and Christchurch were also mobilised, together with a high rise and support appliance The electricity board also attended as the building was under high voltage lines.
The building is a semi-detached industrial unit used as a metal finishing factory. An hour after the first call further assistance was requested and 12 crews attended in all - involving 60 fire fighters. Crews from Hamworthy, Ferndown, Wareham, and Blandford helped fight the blaze.
It is now under control.
More top news
Tuesday evening's weather for the east of the region
Tuesday evening's weather for the west of the region
Highways England thanked people for pointing it out. The A34 sign has now been removed.