The commercial helicopter was contracted by NSW National Parks and Wildlife Service, with the four male passengers all parks staff. They were not seriously injured.

"All five have survived, although two members of NPWS staff and the pilot are reported to have sustained injuries requiring winch rescue," NSW National Parks and Wildlife Service said in a statement.

"NPWS is supporting affected staff and their families."

The contracted helicopter made the emergency landing at 11.30am on Friday after experiencing difficulty north of Lake Crackenback near Guthega Road, within the Kosciuszko National Park.

The Bell 206L helicopter was doing aerial surveying work when it crashed, according to the Australian Transport Safety Bureau, which has begun an investigation.

"A team of transport safety investigators from the ATSB's Canberra central office with expertise in helicopter operations and maintenance is deploying to the area on Friday evening, and is due to be on site from Saturday morning," the bureau said in a statement.

"On site, investigators will examine the wreckage and site surrounds, and will retrieve any relevant components for further examination in the ATSB's technical facilities in Canberra."

Recorded data and interviews with the passengers will be used to publish a report.

NSW Environment Minister James Griffin issued a statement, saying he was thinking of the staff and contractor involved.

"The NPWS family is incredibly professional, dedicated and close-knit, and I know this will affect everyone deeply, as it has me," Mr Griffin said.

"I'll be doing anything I can to support the NPWS staff involved in today's incident, and ensure they, and their families, are supported."

NSW Fire & Rescue personnel are continuing their rescue of the passengers from the crash site, with two understood to still be on the ground as of 4pm.

Firefighters also worked to prevent 150 litres of fuel from entering a nearby waterway.

Police said inquiries have begun into the incident.

Officers attached to Monaro Police District, NSW Ambulance, Rural Fire Service and State Emergency Service crews responded.

Five ambulance road crews and two rescue helicopters with specialist medical crews were called to the scene.

Four NSW RFS members also responded alongside, while two personnel from ACT emergency services attended in the Toll helicopter just before 1pm.