A large vegetation fire that came within five metres of a new Blenheim subdivision and forced the evacuation of 60 homes was deliberately lit, authorities have confirmed.
The fire broke out yesterday on the banks of the Taylor River near West Mount School and has taken 35 firefighters and three diggers to bring under control.
This morning, Marlborough Kaikoura Rural Fire Authority principal fire officer Richard McNamara said crews were working hard to create clear break lines between the trees and the subdivision, dampening down "hot spots" underground.
McNamara said the fire was lit deliberately and there had been no signs that it could have been caused accidentally.
He urged anyone with information to contact the police.
"The area where the fire was started is well used by members of the public so someone must have seen something and we urge them to come forward."
A large scale sprinkler line would meanwhile be installed from George Conway Dr down to the south of the subdivision along the back fences.
A heavy duty grader would also be used to scrape off the dry grass to create a bare earth break and minimise the risk of hotspots spreading.
Sprinklers would run for the next few days to keep the area dampened down.
Access in the area is restricted to residents only.
The Taylor River walkway near West Mount school is closed and members of the public have been directed to stay well away from the area.
A total fire ban remains in place across Marlborough.