Six fire crews were initially attending the blaze on Bay Street, Lansvale, before a further eight arrived later, a NSW Fire & Rescue spokeswoman said.

NSW Fire & Rescue Superintendent Ian Krimmer said the fire started at a timber yard but the exact cause is unknown.

"We had a large factory complex used for the storage of timber and scaffolding," he said. "These pallets of timber have caught on fire producing enormous amounts of smoke."

The blaze began around 3.30pm and was brought under control around 5.30pm.

Just after 9pm, the Fire and Rescue NSW  tweeted that the blaze had been put out, but multiple fire crews will monitor the situation through the night.

LANSVALE |The fire has been ext'd but 6 #FRNSW crews will remain on the scene of the factory o'night to ensure there are no flare ups. — Fire & Rescue NSW (@FRNSW) November 21, 2014

It was earlier feared that the fire would spread to surrounding factories in the complex.

"There hasn’t been any major structural damage at all," Mr Krimmer said. Firefighters battled extreme heat and difficulty getting sufficient water to the site.

"It’s still enormously hot and we’re having to change our crews over very, very regularly," he said.

"We’ve had to pump water from a number of surrounding streets, from fire truck to fire truck here to the fire ground."

The inferno created a large plume of black smoke over the Hume Highway, affecting motorists in evening peak hour.

The industrial site contains a large amount of timber and scaffolding, creating large amounts of black smoke over the Hume Highway, she said.

Earlier, police held fears for nearby residential properties, but the threat abated as the fire was brought under control. Surrounding factories had been evacuated and there was an unconfirmed report that a nearby house had been evacuated, police said. There were no reports of injuries.

According to neighbours, the factory where the fire began is run by the business JJ Auto Parts.

Jim Baba, who works in a complex behind fire site said he was forced to shut down his factory soon after the fire broke out because ‘‘it was too hot and the flames too big’’.

‘‘I was unloading some fabric and I heard some crackers or some fireworks,’’ Mr Baba said.‘‘We could hear explosions from inside [the factory].

‘‘The smell is very bad’’.

Another witness told Fairfax Media that he could smell burning plastic when he called Triple-0 around 3pm.

About 5pm, firefighters cut through wire fencing in an industrial complex to access the back of the factory, where timber crates were still alight.

Ian Krimmer of Fire & Rescue NSW asked motorists on the Hume Highway to keep an eye out for fire trucks, while the Transport Management Centre warned that smoke may lower visibility. The highway remains open but motorists are advised to avoid the area or exercise caution.

Temperatures exceeded 40 degrees in the area Friday, reaching 40.4 degrees at nearby Bankstown and 39.5 degrees at Horsley Park, according to the Bureau of Meteorology.