London (CNN) Grenfell Tower was intended to be among the jewels of an $85 million (£67 million) urban regeneration scheme carried out by the London borough of Kensington and Chelsea.

But on Wednesday, as an enormous fire gutted the 24-story residential block, a series of questions were raised about its safety.

Originally constructed in 1974, the residential tower block had recently undergone a massive $13.2M (£10.3M) refurbishment carried out by private developers Rydon and completed in the summer of 2016.

According to the local authority's website , these large-scale works included the installation of "insulated exterior cladding, new double-glazed windows and a new communal heating system, with the goal of improving energy efficiency."

Notably, redevelopment of the building included provisions for improvements to the " smoke/fire safety and ventilation works ."

Warnings of 'catastrophe'

However, in a blog post dated November 20, 2016 , a residents group, the Grenfell Action Group (GAC), highlighted ongoing concerns among residents over the safety of the building, managed by the Kensington and Chelsea Tenant Management Organization (KCTMO) on behalf of the borough.

The blog post, published after completion of the refurbishment work, argued that only "a catastrophic event will expose the ineptitude and incompetence of our landlord ... 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 post was the latest in a series that dated back to 2013. "We have blogged many times on the subject of fire safety at Grenfell Tower and we believe that these investigations will become part of damning evidence of the poor safety record of the KCTMO," the post read.

In a statement on Wednesday, the management company acknowledged residents' concerns. "It is too early to speculate what caused the fire and contributed to its spread. We will cooperate fully with all the relevant authorities in order to ascertain the cause of this tragedy."

"We are aware that concerns have been raised historically by residents. We always take all concerns seriously and these will form part of our forthcoming investigations."

Photos: Fire engulfs West London apartment block Burning debris falls from Grenfell Tower as a massive fire engulfs the London apartment building early on June 14, 2017. Seventy-two people are confirmed to have died in the fire. Hide Caption 1 of 21 Photos: Fire engulfs West London apartment block Smoke rises from Grenfell Tower hours after the fire. Hide Caption 2 of 21 Photos: Fire engulfs West London apartment block A woman cries as she tries to locate a missing relative. Hide Caption 3 of 21 Photos: Fire engulfs West London apartment block A woman runs near paramedics working near the fire. Hide Caption 4 of 21 Photos: Fire engulfs West London apartment block Witnesses reported terrifying accounts of people trapped in the tower. Some people were reported to have jumped from the tower. Hide Caption 5 of 21 Photos: Fire engulfs West London apartment block People watch as Grenfell Tower is engulfed by fire. Hide Caption 6 of 21 Photos: Fire engulfs West London apartment block Emergency service members work at the scene. Hide Caption 7 of 21 Photos: Fire engulfs West London apartment block Residents of nearby Whitchurch Road watch smoke streaming from the tower. Hide Caption 8 of 21 Photos: Fire engulfs West London apartment block Emergency personnel prepare in an open area near the blaze. Hide Caption 9 of 21 Photos: Fire engulfs West London apartment block People watch as smoke rises from the tower. Hide Caption 10 of 21 Photos: Fire engulfs West London apartment block Michael Paramasivan and his daughter Thea Kavanagh managed to escape the fire. Hide Caption 11 of 21 Photos: Fire engulfs West London apartment block Police officers asked people to step back so they could expand the cordon and make more space for emergency services. Hide Caption 12 of 21 Photos: Fire engulfs West London apartment block Police stand near debris from the fire. Hide Caption 13 of 21 Photos: Fire engulfs West London apartment block A security cordon holds people back as Grenfell Tower burns. Hide Caption 14 of 21 Photos: Fire engulfs West London apartment block Children wear masks that were distributed near the site of the fire. Hide Caption 15 of 21 Photos: Fire engulfs West London apartment block The building, built in the 1970s, was home to 125 families. Hide Caption 16 of 21 Photos: Fire engulfs West London apartment block Emergency services respond to the fire. Hide Caption 17 of 21 Photos: Fire engulfs West London apartment block Firefighters battle the massive blaze. Hide Caption 18 of 21 Photos: Fire engulfs West London apartment block Smoke could be seen billowing over the heads of residents who gathered in nearby streets to watch the blaze. Hide Caption 19 of 21 Photos: Fire engulfs West London apartment block Residents from nearby Barandon Walk wait outside their building. The building was evacuated around 2 a.m. Police told residents that heat emanating from the fire could affect the structure of their building. Hide Caption 20 of 21 Photos: Fire engulfs West London apartment block Witness Michael Kyriakou told CNN the fire spread quickly, with one side of the building ablaze around 15 minutes after it started. "Within an hour it had engulfed the top part of the building," he said. "There are people in bathrobes and slippers all around us, so hopefully as many as possible got out." Hide Caption 21 of 21

Rapid spread of fire

The London Fire Brigade said Wednesday's fire began on the lower floors and spread quickly upwards.

Terry O'Neil, former head of fire engineering at the London Fire Brigade, told CNN that the fire in the building appears to have "spread rapidly from the outside of the building", which was "very unusual."

Christopher J P Miers, an architect and founder of the construction dispute resolution group Probyn Miers, said it was "very concerning" that the fire was able spread so quickly through the building's façade.

Online records show that the company responsible for cladding the building's exterior, Harley Facades Limited, installed "over-cladding with ACM cassette rainscreen."

Miers suggested that the investigation would focus on the ACM (aluminum composite material) panels, what's behind them, and whether the entire exterior wall was constructed to the standards required by the building code.

Mike Gilmartin, director of Omega Fire Engineering Limited, said that investigators would concentrate on how the fire spread so fast. "The question has to be asked how was it able to do so and within a short period of time," he said.

"Of a building of that height we would expect the insulation in the external wall build-up to be of 'limited combustibility'. While it may not have been present in the original construction, consideration should have been given to installing this in the recent refurb."

'Not appropriate to speculate'

Ray Bailey, Managing Director at Harley Facades Limited, said the company would cooperate with the investigation. "There will be many questions about this whole incident and so you will appreciate that it would not be appropriate for us to comment or for others to speculate on any aspect of fire or it causes in advance of these inquiries. At this time, we are not aware of any link between the fire and the exterior cladding to the tower."

Smoke continues to rise from the 24-story residential Grenfell Tower in west London Wednesday afternoon.

Rydon, the main contractor, said the refurbishment work met "all required building control, fire regulation and health and safety standards."

The Royal Borough of Kensington and Chelsea issued a statement early Wednesday saying that its main focus was the rescue operation. "The cause of the fire will be fully investigated and we will keep people informed," it said.

Questions over safety record

Residents' concerns appeared to be focused on the management company's fire safety record.

In October 2015 a fire ripped through another KCTMO property, the nearby 14-story Adair Tower in North Kensington , a "serious incident" according to official reports "which resulted in 16 residents requiring hospital treatment for the effects of smoke inhalation."

After the Adair Tower fire, KCTMO had been issued with two enforcement notices to install "self-closing devices on all flat entrance doors" and review communal staircases and ventilation in the lift lobbies to ensure staircases are "available for use by residents and attending fire crews."

According to minutes of a KCTMO board meeting in November 2016, works to address the issues raised in the enforcement notices had been completed.

The minutes also show that the management company put its fire policy and strategy under review across all of its housing stock.

It raised the need for a "more proactive approach" to fitting self-closing doors, to increase the frequency of fire risk assessments, and to address the issue of "hoarders" -- residents who accumulate materials in their apartments.

The building continued to smolder late in the day.

Located between the wealthy neighborhood of Notting Hill and the White City social housing estate, Grenfell Tower was home to 125 families, according to local councilor Robert Atkinson. Many were council tenants -- residents whose housing is subsided by the local government.

All of the building's 120 apartment units were occupied throughout the refurbishment process, according to the borough website

Dany Cotton, Commissioner of the London Fire Brigade, told reporters that it was an "unprecedented" event in her 29 years of service.

As you will appreciate, this is a completely unprecedented fire. In my 29 years in the London Fire Brigade, I have never seen a fire of this nature, and I have seen many high-rise fires."

"This will of course be subject to a major investigation, but at this moment in time we do not wish to speculate further about the cause of the fire, or the fire's spread. That is something that will be closely looked at in the very near future."