Five people have been taken to hospital after a tree fell on them in Queenstown.

A young boy is critically injured after he was trapped under the branches of a large tree that fell on him and his family in high winds.

A helicopter, ambulances, police and fire services were called to the Shotover Jet headquarters in Queenstown shortly after 1pm on Tuesday.

Two young children, both believed to be under school age, were injured – a boy critically and his sister, who was not seriously injured. Their mother's condition had since deteriorated and she was flown to Dunedin Hospital in a serious condition. The boy's father was also injured.

DEBBIE JAMIESON/STUFF Emergency services work on patients after a massive tree blew over in high winds at the Shotover Jet base, near Queenstown.

The fifth injured person was not a family member.

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Detective Senior Sergeant Malcolm Inglis said an overseas family was standing on the bank watching jetboats when the old willow tree fell.

HELICOPTERS OTAGO A Department of Conservation report says the roots of the tree were decaying.

"There's been a big gust of wind come through the valley and the tree with the wind has collapsed ... and they didn't have time to get out of the way."

The incident was witnessed by several people who came to the aid of the family, Inglis said.

"A jet boat was about to leave when the driver saw what happened he immediately retied and went to assist. Several people came to the assistance of the family to help the young boy trapped under branches and lifted quite a substantial tree from them and rendered medical assistance until emergency services arrived."

GEORGE HEARD/STUFF Five people have been injured after this tree fell in Queenstown.

Inglis said the incident was "just a tragic accident".

A St John spokesman earlier confirmed there were five patients – two in critical condition, one serious, and one moderate and one with minor injuries.

Shotover Jet marketing and communications general manager Kirsty Phillips confirmed a tree had fallen on the bank of the Shotover River.

HAMISH MCNEILLY/STUFF A patient arrives at hospital in Dunedin from the rescue helicopter.

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"The wellbeing of individuals is paramount and our focus is on supporting them, their whānau and our team," she said.

A WorkSafe spokeswoman said they had been notified by Ngāi Tahu Tourism Holdings, which owns Shotover Jet, about the incident but would not be taking further action because the tree was on public land.

DEBBIE JAMIESON It is understood the fallen tree is next to a cafe and reservations building at the Shotover Jet base on Arthurs Point Rd.

A Department of Conservation spokeswoman confirmed the tree was on conservation land, in an area subject to a commercial lease.

"We are currently determining who is responsible for maintenance of trees in this location. In the meantime, our thoughts are with those affected by this accident."

Shotover Jet has closed for the day.

GEORGE HEARD/STUFF Police at the Shotover Jet headquarters in Queenstown.

Otago Regional Rescue Helicopter pilot Kevin Gale said three helicopters, one from Queenstown and two from Dunedin attended the incident.

By the time he arrived at the scene, police, fire and a large number of Shotover Jet staff were assisting the patients.

"I thought it was really well run for the amount of patients and shotover jet staff did a fantastic job of keeping people away. I thought everyone did a great job."