EXPERTS are still trying to solve the mystery of why an aircraft nosedived into the ground after narrowly missing a New South Wales caravan park.

Four people died and two others on board were critically injured when the doomed single-engine Piper Saratoga crashed into a paddock after skimming trees at Moree's Gwydir Caravan Park in the state's north-west.

Stunned tourists and residents from the 150-site caravan park, a member of the Family Parks chain, rushed to the crash site off Blueberry Road and helped pull two badly injured passengers from the wreckage.

Receptionist Kim Ledingham told Caravanning News: "One of our young guys comforted the young girl before emergency services arrived. I heard that the 'plane was very low when it passed over our park."

A preliminary report published recently by the Australian Transport Safety Bureau said an inspection of the wreckage found no anomalies with the aircraft's flight control systems.

The doomed aircraft rests upside down just metres from the caravan park boundary

The pilot's last radio transmission had indicated he was joining crosswind for a landing at Moree Airport's runway 19 but nothing was heard after that, the report said.

"A number of witnesses who were located along the aircraft’s final approach path observed the aircraft flying lower than what they considered was the normal approach profile.

"The aircraft was seen to strike two trees within the boundary of a caravan park to the north of the airport.

"The aircraft subsequently collided with terrain in an inverted, nose-down attitude about 30m beyond the park boundary," it added.

The aircraft's engine and propeller were removed from the accident site and taken to a secure facility for further examination.

Instruments and avionics were also recovered and taken to the Australian Transport Safety Bureau’s facilities in Canberra for technical examination.

The report said investigations into the crash were continuing and would include examination of the aircraft's engine, propeller and other recovered components.

There would also be a review of the aircraft's maintenance records and an examination of the operational procedures affecting the flight.