A suspicious fire at the Wither Hills Farm Park just before noon on Friday happened on the same day signs were put up warning people to stay out of the area during the hottest hours of the day.
Marlborough deputy rural fire officer John Foley said the fire, which started about 11.45am on Friday, was being treated as suspicious.
"We are sort of dealing with the police at the moment, there's nothing else there to pick up on, nothing else there that could have caused it," he said.
Mr Foley said the blaze was a timely warning for people to stay out of the park during high temperatures, when the risk of fire was high.
"Fires in these conditions are going to move pretty quickly and we don't want a repeat of 2000," he said.
Signs put up at entrances to the park by the Marlborough District Council on Friday morning advised people not to go into the park's higher slopes during the hours of 12pm to 7pm.
"We prefer people not even to go up the Quail [Stream track] and the Witches Hat [Rotary Lookout]," Mr Foley, who is also Marlborough's emergency services manager, said.
He urged people to stick to the lower tracks of the hills, where they could get away quickly if there was another fire.
"It's important people understand that a grass fire moves at terrific speed and, once a blaze ignites, the situation quickly becomes serious.
"You cannot out-run a fire travelling fast across the slopes - particularly when the wind comes up," he said.
Crews from both the Blenheim Volunteer Fire Brigade and the Blenheim Rural Fire Force attended the fire on Friday, as did a Marlborough Helicopter, and a Precision Helicopter.
Gaynor McMillan was walking her dog up Forest Park Dr on Friday morning when she noticed flames coming up through the bushes in the scrub opposite Ashwood Dr.
She alerted William Tupoutoa, who had just pulled up at his Forest Park Dr house, and went straight inside to phone emergency services.
"It was just one of those things . . . right place at the right time," Ms McMillan said.
Shaun Maguire was running the same track at the time of the fire when he heard the siren.
"I thought it was a drill and then I got round here and saw the flames," Mr Maguire said.
"It's just great they got it under control . . . if [the wind] was a nor'west that would've just gone," he said.
The signs would remain in place until there was a significant reduction in the fire risk.
- The Marlborough Express
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