A peak motor sport body says it expects the industry will be scrutinised with a " fine-tooth comb " after a car participating in a demolition derby injured 13 people when it crashed into a crowd of spectators at the weekend.

Four people remain in hospital, two of them serious but stable, following the crash at Walcha, in north-west New South Wales, on Saturday night.

Australian Demolition Derby Association (ADDA) president Nathan Williams said the crash could change the face of the industry.

"This is a one-of-a-kind thing that's happened," he said.

Industry scrutiny

Questions still remain over the events that led to the crash, and NSW Police have indicated SafeWork NSW will now be investigating.

Mr Williams said the ADDA did not advise the event organisers.

"We have tried to

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