Thirty Melbourne buildings will be reassessed for fire safety after a burning cigarette sparked a six-storey blaze in combustible cladding on a high-rise apartment building.

Key points: The 30 buildings which are being reassessed were deemed safe in a 2015 audit

The 30 buildings which are being reassessed were deemed safe in a 2015 audit Building experts say many more buildings will need to be audited

Building experts say many more buildings will need to be audited A Senate inquiry last year highlighted concerns about the rigour of safety inspections

The fire at the Neo200 tower on Spencer Street started on a 22nd-floor balcony before quickly spreading up the exterior of the building to the 27th floor.

Firefighters confirmed a discarded cigarette on a balcony sparked the blaze and combustible cladding made from aluminium composite material, like that on London's Grenfell Tower, enabled the fire to easily spread.

Sprinkler systems prevented the fire from moving inside the building.

A discarded cigarette on a balcony sparked the blaze, which quickly jumped five floors of the Neo200 tower. ( Twitter: Bekah Jayne )

Residents remain locked out of the apartment complex as surveyors continue to hold concerns about the building's emergency systems.

A building notice issued on Wednesday says the building's essential safety measures, such as fire pumps, sprinklers and smoke alarms, are "inoperable" or "not working" and residents may be locked out for 14 days.

Residents living on floors not affected by fire or water damage have since been told they could be allowed back by the end of next week.

The ABC understands the Victorian Building Authority (VBA) is planning to inspect a further 30 city apartment buildings that were previously deemed safe to occupy after a 2015 audit prompted by the fire at the Lacrosse building in Melbourne's Docklands in November 2014.

The fire at the Lacrosse building in Melbourne's Docklands in November 2014 prompted a widespread safety audit of Victorian buildings. ( Audience submitted: Wade Savage )

The VBA is writing to owners' corporation managers to inform them that an inspector will visit their property to assess the cladding and fire safety systems.

''In light of the recent fire in Spencer Street, it is prudent for the Victorian Building Authority and the City of Melbourne to review our post-Lacrosse audit," a VBA spokesman told the ABC.

Audit found Spencer Street building 'safe to occupy'

Last year, City of Melbourne's municipal building surveyor served building notices on the Neo200 apartment tower in July and October, requesting owners show cause why the combustible cladding should not be removed.

That was despite the fact the VBA had already deemed the building "safe to occupy" in 2016 following an audit the year before.

On Monday, the chief executive of the VBA, Sue Eddy, said it had adopted a stricter assessment tool as part of the Victoria Cladding Taskforce's statewide audit.

The Grenfell Tower fire in London in 2017 was fuelled by cladding made from similar material as that which fuelled the Spencer Street tower blaze. ( Reuters: Toby Melville )

Building experts believe Monday's fire will prompt the VBA to reassess many more buildings than the 30 buildings initially identified.

"This is not surprising," said Sahil Bhasin, from property inspection company Roscon.

"The risk matrix that's being developed by the Victorian Building Authority will essentially result in any buildings that are audited with a little bit of cladding on there to end up with a building order."

"In 2015 there wasn't much of a criteria or standardised approach. It was independent assessments that were completed. However, the new risk matrix tool that is utilised is too tight."

Concerns about rigour of private safety inspections

The ABC also understands fire safety systems in the Neo200 apartment complex had not been maintained or replaced in years, resulting in the building notice that prevents residents from returning home.

Residents of the Neo200 building could be locked out of their apartments for two weeks. ( Supplied: MFB )

Wayne Liddy, national vice-president of the Australian Institute of Building Surveyors, said apartments were required to undergo regular fire safety checks.

But he said the industry was "unregulated", resulting in residents wasting money with private companies signing off on incomplete work.

"It is regular that we find buildings that have their essential safety measures annual report signed off as compliant when there are aspects that are clearly non-compliant," Mr Liddy said.

"The rigour around the checking and inspection is not as it should be in accordance with the legislation."

The Neo200's sprinkler systems prevented the fire spreading inside the building. ( Supplied: MFB )

"One could look at a report, see that it has been signed off as compliant, but no one is actually doing the investigations to determine … whether the systems were actually inspected and certified."

He said concerns surrounding the industry were highlighted at a Senate inquiry last year.

"I think registration and licensing of participants in that industry is the first mechanism," Mr Liddy said.

"Then annual auditing of the system by the regulator or local council [and] also annual auditing of those licensed and registered practitioners."