The Herald understands the neighbouring VTNZ building has been heat damaged, and the roof and some framing of the Repco building has collapsed because of the intensity of the fire.
A Te Kuiti local said the blaze was a big blow for the area because Repco was a vital business to the town.
Fire and Emergency Waikato assistant area manager Mark Tinworth said quick work by Te Kuiti and Otorohanga brigades saved adjoining buildings from serious damage.
The crews' efforts meant Black Bull Liquor suffered only water and smoke damage, and VTNZ was mostly protected.
"The crews here did a great job with what was required, they stopped the fire from spreading to some surrounding buildings."
The fire was difficult because of the number of combustible materials, including oil, inside Repco.
Crews were now dampening down hotspots, he said.
A Repco spokeswoman said no staff were hurt or on site when the fire started.
"In coming days Repco will be reviewing how we can continue to support our customers in the Te Kuiti area.
"We would like to personally thank those involved in responding so quickly." Videos show smoke billowing metres into the air at the height of the blaze.
Fire and Emergency NZ northern fire communications shift manager Daniel Nicholson said the fire was put out just before 8.30am.
Two fire safety investigators are also at the scene.