Warnings for two bushfires west and north of Sydney have been downgraded as firefighters work to contain the blazes.
A major fire at Winmalee, in the lower Blue Mountains, has burned through more than 1,050 hectares of bushland and was still being controlled on Thursday evening.
But the blaze is not threatening any homes and a "watch and act" warning issued by the Rural Fire Service (RFS) amid strong winds and dry conditions has been scaled back to an "advice".
"By today or tomorrow at the latest we would like to have it contained," an RFS spokesman told AAP earlier on Thursday.
Meanwhile a scrub fire that leapt the M1 motorway on the central coast has plunged commuters into traffic chaos.
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The motorway - formerly known as the F3 - has reopened in both directions at Wyee, and the Transport Management Centre said eight-kilometre queues and heavy delays had subsided.
RFS deputy commissioner Rob Rogers said a fire had jumped the motorway and backburning may be to blame.
"A fire has crossed from the eastern side of Mandalong Rd onto the median strip, then over to the west-hand side," he told Macquarie Network.
"There was a hazard reduction operation in the area, that's certainly - potentially - the cause of it."
He said careful planning always went into the planned burning operations that take place across the 20 million hectares of bushfire-prone land in NSW.
"We don't do these in a cavalier way," he said.
"But when you're doing things like that, occasionally things will go wrong.
The RFS and NSW Police have launched investigations into the cause and origin of the bushfires.
Some Winmalee residents have raised concerns that recent hazard reduction burns in the area by National Parks may have got out of control on Tuesday.
They'll meet with authorities, including police and firefighters, at a community forum on Thursday night.
