A fire investigator has found the blaze started about 4.25pm on Sunday at the Diggalink yard on Weedons Rd, Rolleston, because of a flare-up of hot ash, which had previously been created by a controlled burn-off at the yard.
It spread to a large pile of tyres which was engulfed in flames near State Highway 1.
A Fire and Emergency New Zealand spokeswoman said it took nine engines, eight tankers and a command unit until about midnight on Monday to extinguish.
Multiple diggers and tankers were used to surrounded the fire to keep it contained.