A view of the smoke from Maori Hill. Photo / Mark Downing
Jo McCullough, of Timaru, said she spotted smoke from the blaze on the motorway about 3pm.
About 100 people have gathered at Opoho Park and near the Caledonian Ground to watch.
Rachel Neynens, of Dunedin, called emergency services after spotting the fire about 2.45pm.
"My boyfriend and I were on the athletics track getting ready to do some exercise and we saw some smoke.
"Initially I thought maybe someone was having a bonfire or doing a controlled burn but a few seconds later it was quite big and I saw flames licking a tree."