Firefighters yesterday battled the fire that caused about 500 people, including nearly 30 Illawarra swimmers, to be evacuated from the Sydney Aquatic Centre and engulfed cars in the car park.

Fire and Rescue NSW Superintendent Ian Krimmer said today the latest count indicated 47 cars were destroyed and 33 damaged in the blaze.

Fire Commissioner Greg Mullins said either a cigarette butt or a spark from a car exhaust might have started the fire.‘‘The speculation, pretty strong speculation, is that a small grass fire could have been sparked by a discarded cigarette,’’ Mr Mullins said.‘‘Or it could have been a hot car exhaust setting fire to the tinder-dry grass.’’

Twenty-eight young Wollongong swimmers were stuck at Sydney’s Olympic Park for hours on Sunday night, as their families faced an anxious wait to find out if their cars were among the dozens destroyed in a large fire.

The Wollongong Swim Club members, aged between nine and 16, were in Homebush to compete in the Ryde-Carlile Challenge Cup when a fire swept across a car park near the sporting complex causing numerous cars to explode.

Police told Fairfax Media the number of the number of cars destroyed was likely to exceed 70.

According to swim club president Col Bruton, the Wollongong group remained inside the Aquatic Centre at 8pm on Sunday, while police worked to identify the owners of the burnt out vehicles.

‘‘We don’t know yet if any of the swimmers’ cars are destroyed, but I know that a number of people sometimes park in that particular area,’’ Mr Bruton said.

‘‘I’ve been told by one of the parents that police are not allowing them to leave the centre while they work out who owns the cars.’’

Fire and Rescue NSW Superintendent Ian Krimmer said firefighters were still working to determine the cause of the blaze.

One witness, Todd Fordham, said he saw at least five cars in flames, which caused sporadic explosions and thick billowing of smoke. ‘‘I could hear explosions every 20 minutes,’’ Mr Fordham said. ‘‘There were either tyres popping or petrol tanks exploding.’’

There have been no reports of injuries.

smh.com.au, with AAP