Police and ambulance officers have criticised a hot air balloon company for not calling triple-0 after nine people were injured in a crash in the Hunter Valley.

Key points: It is Balloon Safaris' second crash this year, after four people were injured in January

It is Balloon Safaris' second crash this year, after four people were injured in January NSW Police said would be "common sense" for the company to call triple-0

NSW Police said would be "common sense" for the company to call triple-0 Police said by the time they arrived at the scene, the balloon was gone

Twenty-four people were in the basket of the hot air balloon when it crashed after hitting a tree while trying to land in the tourist town of Pokolbin.

The aircraft, operated by Balloon Safaris, came down on McDonalds Road about 8:00am.

Emergency services were not made aware of the incident until they were contacted by Cessnock Hospital, after nine of the injured arrived at the hospital by private transport.

By the time police attended the scene, the hot air balloon had been removed from the crash site.

Inspector Rob Post, from Hunter Valley Police, said he was unsure what processes the company had in place in the event of a balloon crash, but he would have expected them to call triple-0.

"I think it would be common sense to make that call if you have injured people on the ground," he said.

It is the company's second crash this year — in January four people were taken to hospital after one of their balloons had a "rough landing" near Cessnock, also in the Hunter Valley.

Inspector Post said police had attended the scene of today's crash to gather evidence, but had not yet spoken to the pilot or owner of the company.

"The balloon was gone by the time police had arrived so it wasn't actually on the scene," he said.

When asked if the balloon should have remained in place he replied: "Some would argue, yes."

He said police were not looking to lay any criminal charges in relation to the company's failure to report the crash.

Sorry, this video has expired Authorities speak after hot air balloon crash

NSW Ambulance Inspector Luke Wiseman said nine people were taken to Cessnock hospital.

The injured were aged from seven to 38 years old, and injuries included suspected broken bones.

Two people with suspected spinal injuries were later transported to John Hunter Hospital in stable conditions for additional testing.

Inspector Wiseman said an ambulance later attended the scene to check whether anyone else had been injured.

He said in circumstances where people were injured, it was important that emergency services be called so patients could be properly assessed and triaged.

A hard landing

It had been windy and foggy in the area around the time of the crash.

Three balloons were in the air before the incident, each with about 20 passengers on board, plus a pilot.

The same company experienced hot air balloon crashed in January. ( Supplied: Westpac Rescue Helicopter Service )

Damian Crock, from the Professional Ballooning Association of Australia, has been in contact with the operator and said the incident was regrettable.

He said the balloon took off at about 6:50am and flew for about 30 minutes, however when visibility decreased, the pilot decided to land at the first available landing spot.

"On the approach the balloon contacted trees before landing approximately 50 metres away," he said.

"The balloon landed firmly and some injuries were sustained by passengers in the basket as a result."

Mr Crock said the pilot was "highly experienced" with 3000 hours of commercial flight experience.

"The pilot deemed that there was no need for emergency services to be called."

"As a precautionary measure, three passengers were transported to Cessnock Hospital after the pilot had enquired into each passenger's welfare," he said.

Mr Crock said it appeared that the pilot had descended "faster than he would have liked to be descending" and had then experienced "a hard landing on the ground".

"It's certainly a regrettable incident and people have been injured, so we can definitely confirm that, but their injuries are not life threatening," he said.

Mr Crock said the company "regrets the incident" and "intends to remain in close contact with all the passengers involved and extends [its] apologies to family and friends."

Balloon Safaris is owned by Balloon Aloft, which describes itself as Australia's most experienced hot air ballooning company.

In January's crash, an 80-year-old woman sustained multiple fractures and was trapped in the basket for 40 minutes.

Pokolbin, a popular tourist town, is the epicentre of the Hunter Valley's wine region and about 160 kilometres north of Sydney.

Balloon Safaris has been contacted for comment.