Canberra, Australia: A cockpit voice recorder failed to capture audio of the doomed flight of a light plane that crashed into the roof of an Australian shopping mall last month killing a pilot and four American tourists, accident investigators said on Wednesday.

Australian pilot Max Quartermain, 63, radioed “Mayday” seven times, but did not explain the emergency before the twin-engined Beechcraft King Air B200 plunged into the Direct Factory Outlet mall in the Melbourne suburb of Essendon on February 21 moments after take-off from a nearby runway, the Australian Transport Safety Bureau said in a preliminary report.

He was taking passengers Greg Reynolds De Haven, Russell Munsch, Glenn Garland and John Howard Washburn — who all lived in the Austin, Texas, area — to King Island, 250 kilometres south of Melbourne, on a golfing trip. The bodies of all five were recovered from the burnt wreckage which was strewn across the torn roof and a car park below.

Investigators recovered the so-called black box, which was supposed to record audio in the cockpit in a continuous 30-minute loop. But the cockpit voice recorder had recorded nothing since a previous flight in early January, the report said. The bureau was investigating why the plane’s final moments had not been recorded.

As well as the pilot’s conversation and radio transmissions, voice recorders can record control movements such as flap and gear levers, switch activations, audible warnings and background noise such as the propellers and engines.

Light planes are not equipped with flight data recorders.

The bureau’s Chief Commissioner Greg Hood said investigators had yet to explain the tragedy.

“The extensive damage caused by the collision and post-impact fire has meant investigators are yet to determine a clear picture of the causal factors behind the accident and loss of life,” Hood said in a statement.

Police at the time blamed “catastrophic engine failure.”

Investigators found no pre-existing faults in the wreckage. The engines broke from the wings during the crash and were found in the car park. The engines had been rotating before the crash and there was no evidence of internal components failing, the report said.

The bureau will release its final report on the accident in about 12 months.