Fire investigators believe they have located the point of origin of a major grass and scrub fire on Gisborne's Kaiti Hill on Tuesday night - but how it started is still being investigated.
Much of the city was shrouded in dense clouds of grey smoke over the two hours it took firefighters to bring the blaze under control.
Principal rural fire officer Rene Londeman said further inquiries to establish the cause were still to be made.
"We are still following some leads in relation to it.''
Specialist rural fire investigator Don Scott, the former principal rural fire officer in Gisborne, was contracted to look into the cause of the blaze.
"I have determined the fire started at the base of the hill on the seaward side, in about the middle of the base line of the fire,'' he said.
Mr Scott could not comment on the likely cause.
The firefighters who handled it on Tuesday night did a great job, he said.
"It burned very intensely and they did an excellent job to contain it.''
Police have received information from the public who reported seeing people in Kaiti Beach Road before the fire started.
"We are working to identify those people,'' Sergeant Steve Sutherland said.
Police believe the fire crews involved deserve credit for what they did.
"I thought the firefighting operation went very well.
"They all did a terrific job.''
Mr Londeman said rural fire crews remained on Kaiti Hill last night to monitor the remains of the blaze.
The helicopter flight over the fire scene yesterday morning, using thermal-imaging equipment, identified quite a few `hot spots'.
They were dealt with by firefighters during the day, he said.
"We flew over the area again this morning to make another check.
"Six more hot spots were found and they have been dug out.''
Work continued today to extinguish them, Mr Londeman said.
"We want to make sure the fire is completely out because there are hot temperatures and winds in the forecast.''
The hill will be checked again with an infra-red camera each day for the rest of the week.