A lighter and beer can where among "exhibits" found by police as they investigated the cause of an 800sq m fire on Mauao on Wednesday night.
The cause of the fire was not yet known but a fire chief has said it did not start on its own.
All tracks except the Waikorire track reopened yesterday afternoon after a scene examination was completed by police.
Firefighters were alerted to the blaze at 11.24pm on Wednesday.
Three people were evacuated from the top of the mountain. More than 40 firefighters, six fire engines and two helicopters brought the blaze under control
Yesterday police collected "exhibits" from across Mauao, including a beer can and lighter.
Alan Pearce of Pumicelands Rural Fire Authority said the investigation into the cause of the fire was still ongoing but investigators had found more than one area where they thought the fire could have started.
Mr Pearce said he did not think the fire started naturally.
"One thing about today's investigation - we did not discover a natural cause for that fire, so that raises suspicion, doesn't it? It's not a spontaneous event of nature."
Police were allowed to start their investigation yesterday after the fire crew confirmed there had not been any flare ups overnight.
"There were flare-ups all [Wednesday] night, with flares again on Thursday morning.
"At that stage there was enough fire and heat for it to reignite - which has happened on the Mount in the past."
The police search took about seven hours because conditions were "treacherous", Mr Pearce said.
The Department of Conservation provided a mop-up crew, who carried backpacks of water and tools, to work back and forth across the site to make sure there were no hidden hotspots on the mountain, he said.
Yesterday afternoon control of Mauao was given back to Tauranga City Council and the tracks reopened.
Mr Pearce said caution was taken during the investigation and clean-up because of the difficult conditions on the mountain.
Department of Conservation staff deserved credit for the work they did, he said.
"The ground is very rocky and that is a result of those cliffs falling down in that area ... with vegetation growing in amongst it.
"When you pour large amounts of water on it, it turns into a really big mess. It washes out and it makes the rocks unstable."
Mauao Trust board member Awanui Black said incidents like the fire affected the mauri (life force) of the mountain.
The fire showed wrong practices had been carried out by people in the area, he said.
"The mountain is in direct impact of human activity.
"We need to really consider how our mountain is being utilised, with roughly a million feet going over it every year.
"With the best intentions, these types of disasters still happen."
Every year about 150,000 people reach the summit of Mauao and more than one million people walk around the base of the mountain.
The upper tracks and summit of Mauao, except for the the Waikorire track (the route via the stairs), reopened at 5.15pm yesterday after geologists and abseilers finished their stability investigations.
Geologists would return early next week to complete their final investigations and assessments.
The Waikorire track would remain closed until that work was completed.