Melbourne plane crash: Cockpit recorder did not contain audio
A cockpit voice recorder failed to capture audio from a plane crash that killed five people in Melbourne last month, safety officials have said.
Four US tourists and an Australian pilot died when their light plane came down on a shopping mall on 21 February.
Police initially suggested the plane had "catastrophic engine failure", but a preliminary report released on Wednesday found no evidence of this.
Air crash investigators have yet to find what caused the crash.
Passengers Greg Reynolds De Haven, Russell Munsch, Glenn Garland and John Washburn - all from Austin, Texas - had been on their way to Tasmania's King Island for a golfing trip.
The Australian Transport Safety Bureau (ATSB) will release its final report on the accident in about 12 months.
The preliminary report revealed that pilot Max Quartermain radioed "mayday" seven times soon after take-off from the small Essendon Airport.
The twin-engine Beechcraft King Air B200 crashed into the nearby Direct Factory Outlet shopping centre moments later.
The burnt wreckage was strewn across the damaged roof and a car park below.
The cockpit voice recorder was recovered but officials said it failed to record audio from the plane's final moments.
Light planes are not equipped with flight data recorders.
"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," said ATSB Chief Commissioner Greg Hood.