When they arrived, the fire was out, however the building, Pacific Auto Parts, was filled with smoke, the spokesman said.
A Hato Hone St John spokesman said one person was transported to Dunedin Hospital in a moderate condition.
Crews were at the scene clearing smoke from the building until about 12pm.
The business owner, who declined to be named, said a piece of metal from a car caught fire inside the property.
"Apparently there was a little spark — the staff did really well getting on top of [the blaze].
"The building was very smoky, so Fenz bought their fans to air out the building to make sure it was safe for staff to get back to work.
"The boys were really switched on — [Fenz] have done an amazing job and it could have been worse, but they did a fantastic job getting on top of it."
