Firefighters were continuing to battle the blaze on Wednesday morning - after bringing it under control on Tuesday night - as Newcastle detectives formed a special taskforce to investigate the cause of the inferno.

Newcastle City Police District commander Detective Superintendent Wayne Humphrey, who is the site controller at the Annie Street scene, said on Wednesday the 80-year-old buildings had Super Six asbestos in their roofs.

THE WICKHAM BLAZE:

He said there had been reports from homes west of the fireground - the direction the wind was blowing at the time of the blaze - of some possible asbestos contamination.

The NSW Environmental Protection Authority and Fire and Rescue NSW is investigating the contamination reports and a clean-up of the Soque Apartments on Milford Street - inside another former woolshed building - will take place before evacuated residents were allowed to return home.

"As the rest of the state prays for the rain to go away we're actually pretty happy it's raining at the moment because there's an impact on wetting down asbestos, that's one of the mitigation factors, so that rain is welcome at the moment," Detective Superintendent Humphrey said.

"This asbestos is not radioactive. The rain is helping it, just don't panic, notify and we will work our way through. This rain is washing it away."

A website will be set up for concerned residents to flag their address for further investigation.

Meanwhile, Detective Superintendent Humphrey praised the "incredibly brave" firefighters who were first on the scene after an automatic fire alarm was triggered at about 2.30pm on Tuesday.

He said those firefighters - the first of what would turn out to be about 100 in 30 trucks - tried to battle the blaze inside the building, on the first floor where it is believed to have broken out.

But the flames and heat pushed them outside the building, where they worked to contain the blaze.

The two former woolshed buildings are home to a storage facility along with 12 other businesses. Several people, including the site manager, escaped without injury. Firefighters saved a third former woolshed building on the corner of Annie and Milford streets.

The fire continued to burn on Wednesday under the four levels of floor that had collapsed.

The buildings were structurally unstable, with nothing holding up the external walls - some of which were visibly leaning on Wednesday morning.

A loud crash heard by nearby residents late on Tuesday night was part of one of the brick walls collapsing, a firefighter told the Newcastle Herald.

As the Herald previously reported, the fire took place in a property neighbouring the Ampol fuel storage facility.

FRNSW Chief Superintendent Terry Farley said three tanks containing eight million litres of fuel were as close as 30 metres to the blaze at times on Tuesday.

He said it "would have been catastrophic" if the fire had spread to the fuel tanks.

Chief Superintendent Farley said it could be some days until the fire is extinguished.

Residents of Robert Street have been allowed to return home but people living in Milford and Annie streets remain shut-out. Several roads in the area also remain closed.

Police have set up Strike Force Lynette to investigate the cause of the fire.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: