Firefighters extinguished the last of the flames in the devastating west London blaze as they searched for more victims Thursday, a day after the highrise apartment building fire that killed at least 17 people. Entire families were missing, and the death toll is certain to rise.

Fire commissioner Dany Cotton said authorities genuinely don't know how many people died and firefighters have been traumatized by the inability to save more people.

"Tragically now we are not expecting to find anyone else alive," Cotton told Sky News. "The severity and the heat of the fire will mean that it will be an absolute miracle for anyone to be left alive."

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Firefighters continued to douse hot spots at Grenfell Tower on Thursday, a day after fire tore through the apartment building. (Dan Kitwood/Getty Images)

"I spoke to one of my officers who was very near when someone came out the window, and he was in tears and he is a professional fire officer," Cotton said. "We like to think of ourselves as 'roughty, toughty' and heroes — they are heroes — but they have feelings, and people were absolutely devastated by yesterday's events." 

More than 200 firefighters worked through the night and parts of the building were still seen as being unsafe. Now that the smoke has cleared, the public could only gape at the huge burned-out hulk in the working class, multi-ethnic neighbourhood.

A criminal investigation will be launched into the fire at the 24-storey building, Stuart Cundy of the London Metropolitan Police said Thursday.

Cundy added, "as the police, we investigate criminal offences. I am not sitting here and saying there are criminal offences that have been committed, that's why you do an investigation."

37 remain in hospital

The blaze early Wednesday in west London's North Kensington district also injured 74 others, 17 of them critically, and left an unknown number missing. A tenants' group had complained for years about the risk of a fire.

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Prime Minister Theresa May speaks to firefighters as she visits Grenfell Tower on Latimer Road, North Kensington, on Thursday. (Dan Kitwood/Getty Images)

Up to 600 people lived in 120 apartments in the Grenfell Tower, built in 1974. After announcing the updated death toll of 12 in the afternoon, Metropolitan Police Cmdr. Stuart Cundy said that "we believe this number will sadly increase."

Fire and police officials held another briefing on Thursday to announce the death toll had risen to 17. Of those injured, 37 remained in hospital.

Cotton said it could be weeks before they know exactly how many people died in the fire. 

Prime Minister Theresa May promised an investigation and visited the site on Thursday. London Mayor Sadiq Khan said many questions must be answered about safety for the scores of other apartment buildings around the British capital.

May orders full public inquiry

"But right now, people want answers and it's absolutely right and that's why I am today ordering a full public inquiry into this disaster," she said before leaving 10 Downing Street. "We need to know what happened, we need to have an explanation of this. We owe that to the families, to the people who have lost loved ones, friends and the homes in which they lived."

Nick Hurd, the U.K. policing and fire minister, said it's important that MPs have an opportunity to discuss "this national tragedy."

"And as I said at the top, we must consider it a national tragedy, and that is reflected in the diversity of members of Parliament here representing all parts of the United Kingdom, speaking on behalf of constituencies."

London Mayor Sadiq Khan told reporters while visiting the scene that he welcomes calls for an independent public inquiry.

He said he met residents of the building, as well as friends and family, "who are angry at the lack of answers to what happened."

Grenfell Tower Fire

The London Fire Brigade said it received the first reports of the blaze at 12:54 a.m. local time Wednesday and the first engines arrived within six minutes.

More than 200 firefighters worked through the night at the public housing block. After the heavy black smoke cleared, the public could only gape at the huge burned-out building in the working-class, multi-ethnic neighbourhood.

'It just reminded me of 9/11'

Survivors told of frantic attempts to escape during the nighttime fire.

"The flames, I have never seen anything like it. It just reminded me of 9/11," said Muna Ali, 45. "The fire started on the upper floors.... Oh my goodness, it spread so quickly. It had completely spread within half an hour."

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Food, drink and other supplies are stored beneath an overpass near the fire in west London. More than $1.6 million Cdn has been raised to help victims of the tragedy (Alex Fraser/Reuters)

The Syrian Solidarity Campaign said on its Facebook webpage that Mohammed Al Haj Ali, a refugee from Syria, was one of those who had been killed.

Queen Elizabeth said her thoughts and prayers were with those families who had lost loved ones and with the many people still critically ill in hospital. She also paid tribute to the bravery of firefighters who risked their lives to save others.

"It is also heartening to see the incredible generosity of community volunteers rallying to help those affected by this 
terrible event," the Queen said.

London highrise fire victim remembered9:43

More than $1.6 million Cdn has been raised to help victims of the tragedy as volunteers and charities worked through the night to find shelter and food for people who lost their homes.

Community centres in London have been overwhelmed by the number of donations flooding in for those left homeless. So much food, clothing, shoes and other items have been coming in that the centres, churches and mosques have had to start turning away new donations.

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Emotions ran high as people attended a candle-lit vigil outside Notting Hill Methodist Church near the 24-storey Grenfell Tower, a day after fire gutted the building. (Chris J Ratcliffe/Getty Images)

The cause of the fire is under investigation, and authorities have refused to speculate on what could have started the blaze. But the focus has turned to renovations completed last year that added decorative touches to the building.

The renovation project included installation of insulated exterior cladding, double-glazed windows and a communal heating system. Fire experts say the investigators will need to look at what materials were used in the project and who approved their use.

Questions about building's cladding

The Guardian reports the cladding had a polyurethane core for insulation.

Planning documents detailing the refurbishment did not refer to a type of fire barrier that building safety experts said should be used when high-rise blocks are being re-clad, according to Reuters research.

The government has also promised that other tower blocks which were also recently refurbished would be assessed.

Britain London Fire

Labour Party Leader Jeremy Corbyn arrives to visit the scene of the fire. (Alastair Grant/Associated Press)

Labour Party Leader Jeremy Corbyn said "some very hard questions must be answered."

"The fire is not supposed to spread from one flat to another. It's supposed to be contained. It wasn't — it spread and it spread upwards and it spread outside as well through the cladding," he said.

"Questions on the sprinkler systems, questions on the fire breaks, questions on why the cladding apparently burned, questions on building control regulations, questions on the safety," Corbyn said after meeting survivors and those involved in the relief operation.

With files from Reuters and CBC News