A Robinson R44 helicopter that crashed south of Sydney on Thursday, killing four people, was equipped with fuel tanks susceptible to fatal fires, despite previous safety recommendations.
Australian Transport Safety Bureau (ATSB) investigators at the Bulli Tops crash site have confirmed the Robinson R44 had older-style aluminium tanks which increase the risk of a fatal fire in the event of a crash.
Aviation Safety Investigation general manager Ian Sangston says a decision is being made on whether to issue more urgent safety advice.
"Depending on what is determined over the next several days with the onsite examination, it will be closely re-examined," he said.
Two men were killed last year when another Robinson R44 with aluminium tanks crashed and burst into flames at Jaspers Brush on the NSW south coast.
The manufacturer and the ATSB have previously recommended the model be retrofitted with safer bladder-style tanks, the ABC reports.
December 2013 deadline
In 2010, the manufacturer issued a notice for the fuel tanks to be changed by December this year at the latest.
Aviation Safety Investigation general manager Ian Sangston says a decision is being made on whether to issue more urgent safety advice.
"Depending on what is determined over the next several days with the onsite examination, it will be closely re-examined," he said.
The CSIRO says it believes all four people killed in the crash were staff members who had recently retired.
Witnesses say the four-seater helicopter appeared to have clipped a tree before being engulfed in flames.
Staff at a nearby function centre tried to extinguish the flames and save those on board.
Police say post-mortem examinations have started on the remains of those killed and they are expected to be formally identified in the coming days.
The ATSB says it aims to finalise its investigation within 12 months.