A scrub fire that has destroyed more than 40 hectares of land north of Te Kauwhata is being watched closely as hot winds threaten to cause flare-ups.
Emergency services were called about 5.20pm yesterday to the blaze, which started alongside a railway line in Whangamarino.
Helicopters with monsoon buckets stopped work when it got dark yesterday but resumed this morning.
Waikato Department of Conservation area manager Matt Cook said strong winds were making the battle more difficult.
"The fire started late yesterday afternoon and burnt well into the night. We've knocked it down but have had some flare-ups this afternoon. There's a strong norwest breeze blowing over 20 knots."
More than 40 hectares of Fish and Game-owned land have already been destroyed.
The fire was largely under control but emergency services would likely stay on site until tomorrow to dampen hot spots, Mr Cook said.
While the cause would be investigated, it was believed track grinding work being done by KiwiRail could have sparked the blaze.