A teenager and a man are suspected of starting a fire that has destroyed at least one home in Sydney's west.
The blaze began alongside a nature reserve in the Cranbrook area before spreading to surrounding suburbs on Friday afternoon, the Rural Fire Service said.
It consumed about 300 hectares - destroying or damaging several properties and causing evacuations at schools and nursing homes - before being contained.
A 21-year-old man and 17-year-old boy were being interviewed by police on Friday evening after being arrested at a local service station.
Llandilo resident and business owner Kim Hamilton told AAP the area "often goes up" because of serial firebugs.
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Homes on the NSW south coast also came under threat when firefighters lost control of a hazard reduction burn in the Callala Bay area, near Nowra.
The blaze, which spread over more than 300ha, came within 100m of properties before being downgraded in the evening.
Crews will work throughout the night to contain it.
A total fire ban has been declared in the north and far north coast regions for Saturday.
