Police have confirmed two men aboard a plane that crashed in rugged terrain west of Coffs Harbour in northern NSW have died.

Key points: The two men on board were believed to be in their 50s and 20s

The two men on board were believed to be in their 50s and 20s The rescue helicopter had been unable to winch a rescuer down due to rain and low clouds

The rescue helicopter had been unable to winch a rescuer down due to rain and low clouds NSW SES and police crews were assisting in the search

The wreckage of the plane, which officials said was believed to have a father and son on board, was found in dense bushland about 6.30am on Saturday.

The men, believed to be aged in their 50s and 20s and from the Gold Coast area, were yet to be formally identified.

A search had been underway after a four-seater Mooney M-20 aircraft departed Murwillumbah on Friday morning and did not arrive as planned at Taree two hours later.

The Australian Marine Safety Authority (AMSA) earlier said its Westpac rescue helicopter had located the crash site in the vicinity of Mount Moombil and Dorrigo National Park.

Rescuers located the crash site about 27 kilometres west of Coffs Harbour. ( Supplied: Westpac Rescue Helicopter )

The search area was based on the last contact with the aircraft's transponder that "faded" off the radar about 27 kilometres west of Coffs Harbour.

NSW Police Chief Inspector Brendan Gorman said earlier on Saturday at least 20 personnel from the NSW Police, State Emergency Services (SES) and National Parks and Wildlife Service were assisting in the operation.

The search was sparked on Friday after the plane failed to reach its destination. ( ABC News: Melissa Martin and Claudia Jambor )

AMSA's Sam Cardwell said the crash site was about 500 metres from the nearest trail.

Chief Inspector Gorman said it had been "a very stressful time for the family".

The plane was previously owned by James Sturrock in Western Australia and was sold to a Gold Coast-based purchaser in July.

The small plane left Murwillumbah Airport on Friday. ( ABC News: Donna Harper )

The search was sparked on Friday after associates of the pilot raised concerns about the aircraft not arriving at its destination.

Police had begun knocking on doors around the town of Dorrigo to determine whether any locals had seen the plane in distress.

Chief Inspector Peter Hayes said the residents had been shocked to hear a plane had crashed nearby.

"They're very surprised, it's obviously a flight path that we're looking at and aircraft go over all the time, but you don't expect an aircraft to go down near you," he said.

The Australian Transport Safety Bureau will be responsible for investigating. ( ABC News: Melissa Martin and Claudia Jambor )

Prior to reaching the wreckage, Chief Inspector Hayes had said bad weather had been hampering the search.

"It's very thick terrain, this is the problem, thick and hilly so visibility from the air isn't very good at all due to fog," he said.

"Until the fog clears and we can have a bit of a look as to where the plane possibly went down, that's were we stand at the moment."

The Australian Transport Safety Bureau (ATSB) has been informed and will be responsible for any investigation into the crash.