The fire appeared to have been started by a spark or hot piece of ash igniting sawdust on the roof of a sawdust silo, Mr Tanner said.
"With all this dry weather we've had, everything is tinder dry."
It was rare to get sparks from the kiln fire, which burned continuously, he said.
"It's got on to the rubber belting and away it went."
The fire damaged the conveyor and the roof and some of the silo's walls.
The sawmill is expected to be shut until tomorrow and the kiln until the end of the week.
"We're relieved that although it's serious it's not what you call tragedy and business-destroying," he said. "I'd say it's misfortune but it's not tragedy."
Mr Tanner said he appreciated the truck driver raising the alarm.
"It was somebody from outside [the business] but who knows the sawmill because he comes here in a logging truck sometimes.
"We live in a community where people care about each other. Somebody ringing and telling me there was a fire - we really appreciate it."
Te Puke fire chief Glenn Williams said the first fire crew found part of the plant well ablaze. No one had been on site at the time. Firefighters attended for about two and a half hours.
A hopper at the sawmill was damaged by a large fire started by an electric motor two years ago. The fire caused up to $20,000 in damage and shut the plant for three days.
