A man has been filmed on a local cafe's CCTV footage picking up a large container from outside the Asmara cafe and taking it to a nearby service station. 

The footage then shows him returning at 11.22am, moments before the fire, and walking past the cafe in the direction of the bank.

A short time later an explosion is heard.

5:03pm: Springvale fire chaos streamed live on Facebook

4:44pm; Explosion or fire?

Dandenong CFA operations officer Paul Carrigg said there had been an explosion because of the way the fire was started.

"There's been apparently a flammable liquid used, I'm not sure what the flammable liquid was," he said at the scene.

Was there evidence of an explosion? "Absolutely."

"A lot of flammable liquids will cause explosions".

4:41pm; Three children among hospital patients

A spokesperson for Monash Medical Centre said the Clayton hospital was caring for 13 patients, including three children. All are in a "satisfactory condition".  

She said Dandenong Hospital was caring for 11 adults, including two who have been admitted to a ward for further treatment. The remaining nine are being observed in the emergency department.

The Monash Health hospital network called a "Code Brown" to respond swiftly to the fire. The code, which is called for any external disaster, usually involves the hospital discharging patients who are ready to go home so the emergency departments can send patients to wards, and make space for incoming patients.

"Our Code Brown response was put into action and incident command centres were established at both Clayton and Dandenong," she said.

3:57pm: Security shutters trapped victims

We understand, it took firefighters as little as 90 seconds to reach the scene but they could not get to the victims because the bank's security shutters came down, trapping the people inside. 

3:53pm: What we know so far

It has been just over four hours since a man deliberately lit a fire at the Commonwealth Bank branch in Springvale. Here’s what we know so far:

3:37pm: 'Police surround man in lane'

After witnessing people run out from the bank, passer-by Ernie Gonzalez went out to a lane behind the branch towards his friend's fruit shop.

He said he saw a man, aged in his mid-20s, crouched behind some boxes.

"He was wearing tracksuit pants that were burnt, they looked like shorts," he said.

"His skin was falling off his legs."

Mr Gonzalez said he saw police surround the man before he was taken to hospital by paramedics.

Nearly 30 people have been injured, six with serious burns, in a fire at a bank in Springvale, in Melbourne's south-east.

A man set fire to the Commonwealth Bank branch at Springvale Central about 11.30am, police said.

People were carried from the bank on Springvale Road on stretchers, as paramedics and firefighters treated more than a dozen others on the footpath.

Paramedics have treated 27 people at the scene, including the man who allegedly set the fire.

He has been taken to The Alfred hospital in a serious condition, under police guard.

Five people, who were inside the bank at the time, suffered serious burns. They have been taken to The Alfred hospital, each in a serious condition.

Twenty-one other people, including three children, were treated for smoke inhalation.

Ten people were taken to the Monash Medical Centre, while 11 were taken to Dandenong Hospital for treatment.

Adam Coulshed, a local construction worker who was on site across the road from the bank, said there was a loud bang followed by plumes of black smoke. 

"I thought it was a car accident," he said.

He said his co-worker helped put out the fire with a shopkeeper at a neighbouring Optus store.

The man was trying to get money from an ATM at the time of the explosion, he said.

"It was just black and there were people with blood (coming out of the bank)."

Eric Fleuriot was at Springvale train station when several police cars sped past.

"It's bloody awful," he said of the fire.

"I just can't believe it."

In a statement, the Commonwealth Bank said its "response team" was working with emergency services.

"We can confirm there was an incident at our Springvale branch today. Our first priority is the safety of our staff and customers and as a result the branch will remain closed for the rest of the day," the statement says.

"Our response team is on site and we are working closely with local authorities and emergency services."

Springvale Road has been closed in both directions between Balmoral Avenue and Windsor Avenue.