A preliminary investigation has found the fire started when the Beechcraft Baron aircraft approached a runway at the Kununurra Airport on April 16.
The plane crashed about 800 metres from the runway, killing the nurse who was the only passenger on board and seriously injuring the pilot.
A report by the Australian Transport Safety Bureau found the pilot made an urgent radio broadcast and switched off electrical power after smoke emerged from below the aircraft's instrument panel.
"The pilot then discharged the on-board fire extinguisher at the flames, however the fire almost immediately returned, filling the cabin with smoke and obscuring the pilot's view of the instrument panel and outside environment," transport safety director Stuart Macleod said on Wednesday.
The pilot was able to free himself and the passenger, who later succumbed to his injuries.
"Due to the severity of the post impact fire, ATSB investigators were not able to conduct a complete wreckage examination," Mr Macleod said.
"However, investigators were able to establish evidence of engine rotation prior to impact, while finding no evidence of pre-existing defects to the engines or flight controls that could have contributed to the accident."
Investigators are continuing to determine what sparked the fire and will release a final report at a later date.
But Mr Macleod said there were similarities between the incident and a fire that occurred in the same type of aircraft in 2014 in the Northern Territory.
The bureau has issued a safety advisory notice, urging Beechcraft Baron owners to inspect the aircraft's heater fuel line and ensure electrical wiring is not rubbing and chafing against it.
WA Police in April said a report would be prepared for the coroner.
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