The investigation will also focus on why fire alarms did not go off in certain levels of the 21-storey building to alert residents about to the blaze.

It comes as the MFB confirmed the Docklands fire never appeared on the state government's emergency information incidents website due to a technical glitch.

The feed from the MFB to the emergency.vic.gov.au site - where the public can access live information on emergencies - went down overnight and was not restored until mid-Tuesday morning.

An MFB spokesman Jay Gleeson said they were aware of the "technical glitch" at the time and it did not affect its operational systems.

"There was no threat to the community or restriction on MFB operational readiness due to this outage," he said.

MFB investigators believe the fire started from equipment a resident had "inappropriately" stored behind an air conditioning compressor unit on their balcony on the third floor. It caused the air conditioner to overheat and a fire to spark at 2.24am.

"It was far from being malicious in intent. It would have to be put down as accidental," MFB controller Trevor Woodward said.

The fire it sparked was intense, spreading vertically and quickly up the balconies on one side before it reached the top floor.

"It's very rare that we've had a fire like this that's able to spread vertically so quickly and that will be part of the investigation as well - was it construction or was it something else that allowed the fire to spread?" Mr Woodward said.

"Hopefully there'll be lessons learnt to be put into place and into proposed buildings in the way they're designed."

The units on the side where the fire travelled sustained some fire damage while there was considerable smoke and water damage from internal sprinklers to other apartments.

Mr Woodward confirmed the effectiveness of the building's fire alarms would also be investigated after residents complained that alarms did not go off on some of the floors.

Kathleen Feain, a disability support worker living on the top floor, said the fire alarms had not gone off in her level on Tuesday and nor had they gone off on two previous minor fire events in the past nine months.

"It was just scary. If it wasn't for the sirens of the 19 fire trucks we wouldn't have left. I wouldn't have heard it," Ms Feain said.

Fourth floor renter and software developer Talal Seroor, 25, said the alarms did not got off on his floor either and he was alerted to the fire when firefighters banged on his door to evacuate him.

"We had a drill the Sunday before and it's so loud, but we didn't hear anything," he said.

He was one of about 400 residents who were evacuated first to Southern Cross Station and then to Etihad Stadium where residents were given food, clothes and blankets and were connected to welfare services.

Mr Seroor's apartment escaped damage and he, like many of the residents of Lacrosse Docklands, stayed with friends overnight.

But the apartment complex is home to many international students who did not have friends or relatives to stay with.

Late yesterday afternoon, those people were told they may have to spend the night on makeshift beds in Etihad Stadium if the Department of Human Services, who were working with City of Melbourne, could not find hotels or motels for them to stay in.

Mr Woodward said the apartment's evacuation procedure worked well despite reports of some residents not exiting the building for half-an-hour after the fire started.

With Robyn Grace and Larissa Nicholson