Working through the night, firefighters were struggling on Thursday to reach residents potentially trapped on the upper floors of the Wang Fuk Court housing complex due to intense heat and thick smoke from the fire that erupted on Wednesday afternoon.
The tightly packed complex in the northern Tai Po district has 2000 apartments in eight blocks, housing more than 4600 people.
By Thursday morning, authorities said they had brought the fire in four blocks under control, with operations continuing in three blocks.
Video from the scene showed flames still leaping from at least two of the 32-storey towers sheathed in bamboo scaffolding and green construction mesh, as heavy smoke billowed into the sky.
Police said in addition to the buildings being covered with protective mesh sheets and plastic that may not meet fire standards, they discovered some windows on one unaffected building were sealed with a foam material, installed by a construction company carrying out maintenance work.
Three men from the construction company, two directors and one engineering consultant, had been arrested on suspicion of manslaughter over the fire.
The green construction mesh and bamboo scaffolding used on the buildings are a mainstay of traditional Chinese architecture but have been subject to a phase-out in Hong Kong since March for safety reasons.
A firefighter was among the 44 killed, with 45 people in hospital in critical condition, Hong Kong police told a press conference before dawn on Thursday.
The death toll is now the highest in a Hong Kong fire since 1948, surpassing the 41 killed in a blaze in a commercial building in the Kowloon district in November 1996.
The latest fire has prompted comparisons to the Grenfell Tower inferno that killed 72 people in London in 2017. That fire was blamed on firms fitting the exterior with flammable cladding, as well as failings by the government and the construction industry.
Some 279 people were uncontactable and 900 were in eight shelters.
Many residents took to social media to criticise what they saw as negligence and cost cutting as a cause of the fire. One video showed several construction workers smoking on the bamboo scaffolding surrounding one of the complex's blocks during the renovation process.
From the mainland, China's President Xi Jinping urged an "all-out effort" to extinguish the fire and to minimise casualties and losses, China's state broadcaster CCTV said.
On Thursday, frames of scaffolding were seen tumbling to the ground as firefighters battled the blaze, while scores of fire engines and ambulances lined the road below the development.
Hong Kong's government moved to start phasing out bamboo scaffolding in March, citing worker safety after 22 deaths involving bamboo scaffolders between 2019 and 2024. It announced that 50 per cent of public construction works would be required to use metal frames instead.
Though fire hazard was not cited as a reason for the phase-out, there have been at least three fires involving bamboo scaffolding this year, according to the Association for the Rights of Industrial Accident Victims in Hong Kong.
Hong Kong's sky-high property prices have long been a trigger for social discontent in the city and the fire tragedy could further stoke resentment towards authorities ahead of a city-wide legislative election in early December.
Wang Fuk Court is one of many high-rise housing complexes in Hong Kong, one of the most densely populated areas in the world. Tai Po, located near the border with mainland China, is an established suburban district with some 300,000 residents.
Occupied since 1983, the complex is under the government's subsidised home ownership scheme, according to property agency websites.Â
