A coroner is unable to determine the cause of a fire that destroyed 47 cars at Sydney's Olympic Park.

The fire in a car park outside the Aquatic Centre at Olympic Park in Homebush destroyed 47 cars and damaged dozens of others on October 13, 2013.

Coroner Helen Barry said the car park was full and it was a hot and windy day with a total fire ban in place.

She said the fire started on a garden bed of drought-affected plants and spread quickly but she was unable to determine if it started from a discarded cigarette butt.

Glebe Coroner's Court heard CCTV did not capture ignition of the fire but did capture it spreading.

Ms Barry said staff with fire extinguishers were not able to put out the fire so the Aquatic Centre was evacuated.

Firefighters battled the blaze which was driven from car to car by strong winds. ( ABC )

"About 3:00pm the P2 Sydney Olympic car park was operating at full capacity due to both an aquatic carnival and an athletic carnival. There were approximately 3,500 people at the Aquatic Centre," she said.

Two civilians and firefighters were treated for minor injuries, 47 cars were destroyed and a total of 105 damaged.

The damaged vehicles were primarily in the staff car park and P2 car park.

The coroner said there were eight fire hydrants in the park and fire crews from Lidcombe, Rhodes and Silverwater had been involved in "pre-incident planning " for Olympic Park.

But she said on the day of the fire, Ashfield Station crews responded to the fire because the other crews were working elsewhere.

The coroner said it took the Ashfield crews up to 10 minutes to find the fire hydrants and recommended fire hydrant plans be made available to more fire stations around Olympic Park.

She said better signs might also help crews find fire hydrants more quickly.

Ms Barry said the fire started behind a car in the P2 car park and while there was a suggestion it might have been started by a discarded cigarette butt, this could not be established conclusively because "no such material was discovered at the scene".

"Unfortunately, even though it is an offence to discard cigarettes or butts, there is little that can be done to prevent the actions of some persons who disregard the law and the safety of the community," she said.