Crews to stay overnight as blaze continues

Firefighters battling a blaze at a Sydney tyre and car repair factory are expecting to battle it for a second night.

Four fire trucks arrived at Brooks Tyres in Church Street, North Parramatta about 8:40pm on Friday but quickly had to call in another 12 units as flames intensified.

"Tyres burn very well and they are very hard to put out," a NSW Fire and Rescue spokesman told AAP.

Despite crews rotating four-hourly to mitigate the effects of hot weather and defensive fire-fighting, one man was taken to hospital on Saturday with heat exhaustion.

NSW Fire and Rescue says it doesn't yet know the cause of the fire, because investigators have not been able to inspect the site.

"Last night the consensus was that it did not look to be suspicious," the spokesman said.

Firefighters were getting "on top" of the fire with just five trucks by mid-Saturday afternoon but are still expecting to be fighting it through the night until Sunday morning.

They have been working hard to ensure the flames do not spread to a neighbouring smash repair business, the fire spokesman said.

Engineers are on scene to monitor the building for movement and potential collapse.