A stone flicking around in a baler is the likely cause of a hayfield fire on Thursday evening in South Wairarapa.
A Featherston fire crew were dispatched to No.1 Line near Tauherenikau shortly before 8pm to contain a spreading fire among the stubble.
Several hay bales were well alight by the time the crew arrived.
It took about half an hour for firefighters to get the blaze under control.
Farmhands were dispersing and spreading the blazing bales with a front-end loader so they could be hosed down.
The Carterton fire brigade's water tanker backed up the Featherston crew.
Contractor Tim Lindon, of B&B Contracting, said he thought a stone in his baler had sparked the fire.
"It got going quite quickly," he said.
"We emptied the fire extinguisher, and figured it was too big."
He said he had never experienced it before.