Watch: Falling tree injures two people, damages four cars in Auckland's Cornwall Park

A tree that fell on four cars, injuring two people, in a popular Auckland park this afternoon, had recently been assessed as having only a one in a million chance of falling.

Witnesses have described the "almighty rumble" when the 30m cottonwood tree fell over in the full carpark of Auckland's Cornwall Park just below the restaurant and information centre at about 2.15pm.

A woman and her son-in-law suffered moderate injuries, and were taken to hospital.

One witness described the incident as "like a mini earthquake".

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Cornwall Park management and the Cornwall Park Trust Board issued a statement this evening, saying they were "very concerned" by what happened.

"Our sympathies go to the people directly affected by this accident for whom it must have been a considerable shock," park director Michael Ayrton said.

The park has commissioned an immediate arborist report on what had happened with the tree, he said.

All trees in the park are independently audited every 12 months by arborists who assess and grade the risk of a tree or limb fall, Ayrton said.

The tree that fell today had been assessed as having only a one in a million chance of a fall, the statement said. Trees with higher risk assessments are removed.

Cornwall Park Bistro restaurant manager Lance Ourednik was at work when the incident happened.

"It felt like a mini earthquake," he said.

"There was a massive crack [sound] then a few seconds later a smash, when it hit the glass of the windscreen."

The woman was trapped in the car by the tree trunk, Ourednik said, which a group of men removed to pull her out of the vehicle.

Bevin Adamson was having a family picnic in the park when he heard an "almighty rumble".

"It sounded like the loudest thunder I have ever heard.

"A few seconds later car alarms started going off left, right and centre."

Amanda Norwood was at a child's birthday party with her husband and son when she heard what she thought were fireworks.

"So we turned around and it was more like a landslide, it looked like a whole lot of earth was just moving but it was just all the branches just falling down and pulling down the branches from the tree in front of it as well.

"I guess all the noise was the glass from the cars and so forth."

Norwood's grabbed her son and her husband rushed over to remove a branch off a lady who was standing beside her car when the tree fell.

The couple had parked in the car park where the incident happened.

"It's anyone's worst nightmare thinking about what could've been," Norwood said.

"I've never seen anything like that. The whole tree was completely uprooted...it was huge and there was quite a lot of damage. We couldn't believe more people weren't hurt."

The two people suffered moderate injuries and no one was trapped in the cars, a police media spokesperson said.

Earlier, Ayrton told the Herald a woman was taken to hospital in an ambulance and was accompanied by her son-in-law who also had some minor cuts.

They were both in shock, he said.

Workmen clean up after a large tree crushed multiple cars in Cornwall Park. Photo / Dean Purcell

Some of the vehicles had been quite badly damaged with the roofs being crushed and the windscreens smashed, Ayrton said.

"I am unsure of what caused the tree to fall.

"We had windy conditions today but the tree is in a relatively sheltered part, so I was quite surprised."

A Norfolk Pine tree next to the tree that fell was badly damaged and might need to be removed, Ayrton said.

The cars were being towed away and the surrounding area was being cleaned up by staff.

The road leading to the carpark was closed and the tree was still lying across the carpark.

The tree was 130-years-old and was in a relatively sheltered position in the park.

Consulting arborists were on site to try to establish what caused the tree to fall. The 8000 mature trees at the park are inspected annually by an independent arborist and daily by park staff.

An independent arborist will be assessing the tree tomorrow and those in its immediate vicinity, said Ayrton.

"We are just relieved no one was seriously hurt."

A similar incident happened in February this year when another tree fell at Cornwall Park, crushing a number of cars.

In that incident a woman was treated for shock.

All trees in the immediate vicinity were assessed after the incident in February, Ayrton said, and minor maintenance work was undertaken.