The London apartment building that was engulfed in a deadly blaze early Wednesday has been the subject of resident complaints over fire safety for years.

Grenfell Tower, a 24-story building made up of 120 apartments, is believed to have had as many as 600 people inside it when the fire broke out on one of the lower floors. It is a public housing unit in the North Kensington neighborhood of London -- one of the British capital's most affluent areas.

An action group for the building's residents had complained on its blog of lax fire and safety standards at least eight times during the past three years, accusing the site's landlords, the Kensington and Chelsea Tenant Management Organization (KCTMO), of mismanagement and neglect.

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In a post from November 2016 entitled, "KCTMO -- Playing with fire!" the association said, "It is a truly terrifying thought but the Grenfell Action Group firmly believe that only a catastrophic event will expose the ineptitude and incompetence of our landlord, the KCTMO, and bring an end to the dangerous living conditions and neglect of health and safety legislation that they inflict upon their tenants and leaseholders."

The blog post continued: "It is our conviction that a serious fire in a tower block or similar high density residential property is the most likely reason that those who wield power at the KCTMO will be found out and brought to justice!"

Former head of the Grenfell Tower Residents' Association, Damian Collins, told the AFP news agency Wednesday that building residents had voiced concerns about a lack of fire exits and faults in Grenfell Tower's heating and lighting systems, but that they were ignored.

"There were so many concerns," he said. "The telling thing this morning was that when I woke up, I wasn't surprised... Shocked, terrified for all the people living here, not surprised."

"If the same concerns were had in a wealthy part of Kensington and Chelsea they would have got resolved, but here they didn't get resolved," Collins said.

One young resident who escaped Wednesday's blaze told CBS News that she saw the flames spread rapidly throughout the building.

"Six minutes it took for the fire to reach six floors above the fourth," where she said it seemed to have begun. "All you could hear was people screaming 'help,' and you could see flashlights because it was dark. You could see flashlights from the windows showing that people were still at home. People were screaming, banging on the windows," she told CBS.

Another witness told Sky News that the "fire climbed up the side of the building ... as if it was paper. It flew up. It was horrifying."

Smoke billows from the Grenfell Tower apartment building after it was engulfed in flames in North Kensington, London, June 14, 2017. REUTERS

Fire safety expert Dr. Angus Law put out a statement saying, "early media reports suggest that this even has similarities with other fires that have occurred recently around the world; it appears that the external cladding has significantly contributed to the spread of the fire at Grenfell Tower."

The building's external cladding was installed as part of a massive refurbishment completed by the company Rydon in May 2016, the handling of which residents had also complained about.

Rydon issued a statement late Wednesday saying their work, "met all required building control, fire regulation and health & safety standards."

Some residents who had made it out onto the street reported having been advised to stay in their apartments in the event of a fire.

According to a newsletter sent to residents by KCTMO in May 2016, this would have been in line with the building's "stay put" fire policy at that time.

"The Fire Brigade has asked us to reinforce the message that, if there is a fire which is not inside your own home, you are generally safest to stay put in your home to begin with; the Fire Brigade will arrive very quickly if a fire is reported," the newsletter said.

"The only reason you should leave your home is if the fire is inside your home... If there is a fire in the block near your flat, and you believe you are at risk and would prefer to evacuate the building, then please do so using the stairs and wait outside the building for the Fire Brigade to arrive," the newsletter continued.

Responding to questions about Grenfell Tower's fire safety standards, London Mayor Sadiq Khan told the BBC on Wednesday that, "what we can't have is a situation where people's safety is put at risk because of bad advice being given or, if it is the case, as has been alleged, of tower blocks not being properly serviced or maintained."

London's fire commissioner Dany Cotton called the fire, in which at least six people were killed, an "unprecedented event," saying it was unlike anything she had seen in her 29-year career.

"There are kids that are literally just being thrown out of the balcony, people throwing themselves out of the balcony just so they don't get burned," resident Samira Awil told CBS News. "They thought that the fire brigade, the ambulance, the police would be able to catch the kids. Panic set in… there were a lot of casualties. A lot of bodies."