5.28pm: Help is being sought from members of the public to establish the cause of a fire on Mauao overnight.
In a statement, Tauranga Police, the New Zealand Fire Service and the Rural Fire Authority said they were asking people to come forward with any information.
Detective Senior Sergeant Greg Turner said police were aware there were a number of people on Mauao that evening, including several mountain bikers.
Mr Turner said police would like those people, and anyone else who may hold information about the fire, to contact the Tauranga Police.
A scene examination is to take place on Friday once it is safe for staff to access the scene.
Anyone with information is asked to contact Tauranga Police on 07 577 4300.
Information can also be provided anonymously to the organisation Crimestoppers on 0800 555111.
12.19pm: Earlier indications that Mauao would open later tonight have been dashed.
Tauranga City Council said Mauao would be completely closed until at least midday tomorrow, pending feedback on rock fall risks and potential hotspot flare-ups.
Council communications manager Aimee Driscoll said NZ Fire Service would continue monitoring the site this afternoon and into the evening, with helicopter crews standing by to dampen any flare-ups.
Ms Driscoll said Adams Avenue was now open.
11.10am: The Mount base track will likely re-open tonight, while Waikorire track (purple line in map below) remains closed for at least two days.
Council spokeswoman Emma Cottin said for now all tracks remain closed and asked the public to steer clear of the area until further notice, while the stability of the rocks has been thoroughly assessed and confirmed by council contractors.
She expected Adams Avenue to reopen around midday today.
Helicopters have stopped dropping water, after dumping over 40,000 litres of water over the fire. Firefighters and a DOC fire crew have set out on food to assess the situation.
Ms Cottin said the firefighting water line on Mauao had proved very efficient, allowing to fill the monsoon buckets close to the fire location and therefore contain the fire faster.
The water line brings water from the main reserve on the east side of the Mount and feeds a number of hydro points.
Ms Cottin said the fire was not a threat to Beachside Holiday Park occupants.
10.50am Western Bay police tactical response manager Karl Wright-St Clair said the Fire Service's fire safety officer was not able to get onto the site yet to investigate because it was still too dangerous.
"We are waiting for the Fire Service to let police know when they will be able to go onto the site and we will accompany them, and look at it from there.
"Until we know what we are dealing with, we don't know if or where the investigation will go," Mr Wright-St Clair said.
Long-time Mount resident and conservationist Allan Goodhall said the fire highlighted how Mauao was such a fragile and important environment.
"It is so important in so many ways to so many people," he said.
Whether they were walking around the base track or up and down Mauao, whether they were members of the wildlife trust, or people working out - Mauao was so well used, he said.
"Luckily it was no where near the extent of the 2003 fire," Mr Goodhall said.
10am: A man fishing on Salisbury Wharf said he saw a bright flare land high up on Mount Maunganui before a fire erupted in the same spot.
Ryan Biggar said he was sitting with mates on the wharf when he saw a green flare light up the night sky and head towards the side of the mountain.
"We just saw it go up and it just sailed down in an arc direction.
"The fire started where the flare landed a couple of minutes after we saw it."
Mr Biggar said the fire did not take long to become an enormous blaze that spread quickly up the mountainside.
He could not tell if the flare had been set off on the land or from the water.
8.44am: Three people had to be rescued from Mauao overnight as fire, possibly started by a flare, took hold of the mountain.
New Zealand fire service assistant area commander Aaron Waterrous has confirmed reports of a flare sighted at Mauao just before the fire began.
Mr Waterrous said when firefighters arrived, there were three people on the Mount.
Firefighters prioritised getting those people down from Mauao. Once they were successful they were then able to focus on the blaze.
Mr Watterrous would not comment further on the people.
8.17am: Mount Maunganui has been closed until further notice.
Can we please ask people, for their own safety, to stay way from the area until further notice.
Tauranga City Council communications manager Aimee Driscoll said no one had been harmed in the "medium-sized" fire that broke out on the Mount yesterday night and there was no current risk to campers.
The fire's cause is unknown but it has been contained though not completely out.
Two helicopters with monsoon buckets are dousing the fire, with a third on standby.
Tauranga City Council acting manager parks and recreation Warren Aitken said they hoped the fire would be out by this morning, with a number of hours after to dampen it down.
"Once the fire is fully extinguished we will need to assess the stability of the rocks to ensure they are safe before we open the area up to the public.
"We have cordoned-off the area, closed road access and have security onsite. Can we please ask people, for their own safety, to stay way from the area until further notice," Mr Aitken said.
7.34am: Two helicopters continue to battle the scrub fire on the eastern side of Mount Maunganui this morning.
Each helicopter is able to carry 600 litres of water and alternatively each one is dropping massive buckets of water on the Mount every 60-90 seconds.
By 8am the helicopters have already dropped 53 buckets containing 600 litres of water.
The 800-900 square metre patch on the Mount is still smoking but New Zealand fire service assistant area commander Aaron Waterrous said the helicopters would work for another hour before ground crews would get onto the Mount to tackle the fire by foot.
5.45am: The fire broke out just before midnight and has been burning since.
So far it has destroyed vegetation on the northern side of the landmark Bay of Plenty mountain.
Mr Waterreus described tackling the mountain-top blaze as extremely dangerous and posing difficulties for firefighters.
"It's quite steep terrain up all sides of the mountain so we have to be very careful.
"It's obviously dangerous, night-time, steep ground and it's on fire. It's a very dangerous situation and we have to be careful."
Right now.. pic.twitter.com/WAxxAFxAil— Mount Maunganui (@Mt_Maunganui) January 13, 2016
He said the size of the fire and flames were quite impressive.
Thanks to favourable conditions the fire had been contained to a relatively small area.
It was hoped the fire would be out by early afternoon.
The fire service would be conducting a full investigation to determine the cause of the blaze.
In recent weeks, there has been a spate of arson attacks in the Tauranga and wider Bay of Plenty region, with several schools being targeted.
Last month saw the fire service attend to fires at three schools, including Merivale Primary School and Arataki School.
Radio New Zealand reported that an eyewitness had told police they saw what appeared to be either a lantern or a firework fall onto the Mount.
Fire Service northern shift manager Scott Osmond said around eight fire crews were battling the fire.
"In that area it's very steep country and it's simply inaccessible. All we can do is try and contain it without it spreading too much," he said.
Jody McGinity, who is camping at Papamoa, said last night the fire could be seen from the campground, about 16km away from Mt Maunganui.
"We were just sitting having a drink and then we wondered what the light was," she said.
They then realised it was a blaze, and called the Fire Service.
"It's spread about half way down the right hand side [of the Mount]," Ms McGinity said.
The large fire was spreading quickly, because of a strong breeze.
"It looks really bright."
Hamilton holidaymaker Jody McGinity, who is staying at a nearby campsite, said the mountain was looking ominous at daybreak.
"It looks dark on the top of the mountain this morning," she said.