Constable Aaron Ridaelli said the Warren Rusbridge Transport Wanaka truck was travelling from Queenstown to Wanaka via the Kawarau Gorge about 11am yesterday, when the trailer (pictured right) overturned, strewing logs across the road.
"It's unclear how it rolled.
"It just jumped up and turned around somehow.
"It's a bit of a mystery at this stage," he said.
The truck had just come around a moderate right-hand bend when the crash occurred.
The driver pulled into the left-hand side of the road with the trailer still attached.
The driver was uninjured and the logs did not hit any other vehicles on the road, he said.