An emergency order will prevent residents of a Melbourne apartment complex from returning to their homes after fire spread up the side of the high-rise building, which firefighters say has combustible cladding similar to the material used on London's Grenfell Tower.

Key points: Firefighters believe the building was clad in similar materials as London's Grenfell Tower

Firefighters believe the building was clad in similar materials as London's Grenfell Tower Fifteen trucks and 60 firefighters were sent to tackle the high-rise blaze

Fifteen trucks and 60 firefighters were sent to tackle the high-rise blaze A man was treated for smoke inhalation but no-one was seriously injured

The fire started on a 22nd-floor balcony of the 200 Spencer Street building shortly before 6:00am, and spread up the exterior of the building to the 27th floor, firefighters believe.

Fifteen fire trucks, two ladder-platform trucks and 60 firefighters were used to extinguish the fire, which was brought under control at 6:49am.

Metropolitan Fire Brigade (MFB) chief officer Dan Stephens said firefighters believed the building was clad with similar materials as London's Grenfell Tower, in which 72 people died in 2017.

"My understanding is that the building is cladded with aluminium composite materials (ACM) … so the sort of cladding that was on the Grenfell Tower," he said.

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He said fire investigators would determine how the blaze started and spread.

"I can't speculate at this time, what I can say is that there's evidence of external fire spread," he said.

"We do know that because the sprinklers were activated, that the fire has penetrated internally [as well]."

Sprinklers were activated on four floors of the building, and firefighters said it was unclear how badly the apartments would be damaged.

Residents will be allowed to return to their homes for a short period of time to get belongings and medicines but will be barred from staying there for 48 hours until fire safety systems are repaired and in working order.

The order was issued by the City of Melbourne after about 150 people were evacuated earlier.

A man in his 20s was treated for smoke inhalation at the scene by paramedics and taken to the Royal Melbourne Hospital in a stable condition.

The City of Melbourne said about 200 people had visited a relief centre set up at the Melbourne Town Hall.

Mr and Ms Edman it was an "overwhelming experience" and they just want to go home. ( ABC News: Karen Percy )

'Lucky to get out of there'

Caroline and Clem Edman were among those evacuated.

The couple were holidaying in Melbourne from Victor Harbour, south of Adelaide, and had booked the 14th floor apartment through Airbnb.

"We heard the evacuation order and we sort of took off basically in the clothes we were in," Ms Edman said.

"The flames were quite fierce when we got out and had a look, you could see them pouring out of the windows upstairs.

"It's been quite overwhelming. We just want to go home."

Mr Edman said there was a strong smell of smoke when they were allowed back in hours later to collect their belongings.

"Just long enough to grab our stuff real quick and get out, that's all we had time to do," Ms Edman said.

"[There's] a little bit of smoke damage around in the corridor, on the mirrors and the lighting is all emergency-grade lighting, so you can't see a lot.

"The fire guys were telling us that above us there's either smoke damage or water damage and some places are uninhabitable.

"I just think how lucky we were to get out of there."

Fire investigators and building surveyors examined the building. ( ABC News )

Some residents refuse to leave

About 150 occupants were evacuated from the building immediately after the fire broke out, but firefighters said some had refused to leave.

"We're a bit concerned about some of the occupants who have resisted our advice to evacuate the building," assistant chief fire officer Trent Curtin said.

He said firefighters had discovered some residents had put plastic over their smoke alarms to stop them going off while they were cooking.

"We're really concerned about some of the fire safety aspects we're seeing," he said.

"Anyone who covers their smoke alarm with plastic is putting themselves and other occupants of the building in danger."

Adam Dalrymple, the MFB's acting deputy chief officer, said the building would have been assessed by the City of Melbourne and other agencies to determine compliance with the building code.

But he said the MFB disagreed with the level of cladding allowed under current building codes.

"Our view is that any building with an effective height over 25 metres shouldn't have cladding on it at all," he said.

The ABC understands that the City of Melbourne issued two show-cause notices in July and October last year to the property's owners over concerns the cladding was combustible.

Under the notices, owners were asked to prove why the cladding should not be removed.

Modifications to fire safety measures were made, including the installation of additional smoke alarms, but the cladding remained.

A City of Melbourne audit of high-rise buildings recently found 51 per cent had non-compliant cladding.

Occupants 'in shock'

People evacuated from the building told the ABC they woke to a fire alarm and the smell of smoke.

"We thought that there would be a proper evacuation plan, but there was no plan, nobody was there to direct," Kimmy Sinsinwar said.

Mr Sinsinwar, who was staying at an Airbnb-rented apartment in the complex with a woman and young child, said he did not hear any specific warning besides the fire alarm.

"Being inside the building, you don't know how bad it is or what's going on so we were kind of in shock with the little one," he said.

Aaron Duncan, who lives in the complex, said the fire brigade used a loudspeaker to tell residents to evacuate about 6:00am.

"It's interesting to know the fire alarm's probably not as loud as I thought it would be," he said.

Residents were waiting to find out when they could return to their apartments. ( ABC News )

Michael Williams said he only heard the fire alarm after most residents had left the building.

"We didn't hear the alarm until about 15 minutes ago. We thought it was a few blocks down," Mr Williams said.

"[I] then came out and had a look down and saw all the fire trucks and thought, shit, we'd better get out.

"It was pretty scary.

"It was smoky through the stairwell and then when we heard it was on the floor that we were supposed to be on we thought, someone's looking after us."

Flammable cladding 'exactly' where fire spread

A forensic building inspector said images of the tower's exterior suggested there was a line of flammable cladding in panels where the fire broke out.

"This building is extremely safe, it's around 90 per cent made out of concrete panel construction, there's only about a 10 per cent mix of ACM panels," Sahil Bhasin told ABC Radio Melbourne.

"They are sadly exactly where this fire broke out."

Sahil Bhasin said a vertical strip of flammable cladding on the building aligned with the spread of the blaze. ( Supplied: Sahil Bhasin )

The MFB warns residents in high-rise buildings to exercise extreme caution on balconies due to the risk of fires spreading vertically through flammable cladding.

Mr Bhasin, who is the general manager of Roscon, said it appeared the building's fire plan had worked "perfectly".

"The fire occurred, the sprinklers came on and, assisted with the MFB, the fire was doused."

A Victorian Government audit conducted after the Grenfell Tower disaster found flammable cladding posed a fire risk on 1,400 buildings.

Rectification works on those buildings were likely to begin in the next 18 months, Mr Bhasin said.

Even removing cladding from every second storey of those buildings could reduce risk by creating "firebreaks", he said.

Building managers said building was 'fully compliant'

The Neo200 apartment complex was found to be "fully compliant" with cladding standards in 2017, according to a tweet from the building managers.

"While most of the building is not clad at all, where any cladding is used it is compliant with VBA [Victorian Building Authority] standards," Neo200 tweeted in June 2017.

Neo200 was built by L.U. Simon Pty Ltd, which also built the Lacrosse apartment tower in Docklands, where fire raced up flammable cladding in 2014.

The Neo200 website describes the apartments as "the very best in contemporary, inner-city living in a truly dynamic location" on the western end of the CBD.

Firefighters said the blaze spread up and across several storeys. ( ABC News )

Premier Daniel Andrews said he would wait for an investigation into the fire before making comment on the role flammable cladding played in fuelling the blaze.

"On the issue of Spencer Street, let's get the facts," he told ABC Radio Melbourne.

"We might be able to talk more fully then."

Mr Andrews said his Government understood there was "more to do" following the audit of cladding in Victoria.

"That includes both the fire response, inspections, the building code framework for the future so we don't see any more buildings built either with the wrong cladding or misusing cladding that is in fact ok in its nature," he said.