It is the deadliest fire Hong Kong has seen in decades.
At least 44 people have died and hundreds have been reported missing in a massive blaze at the Wang Fuk Court housing complex in Tai Po district.
Several dozen others have been hospitalised and 45 remain in a critical condition.
Hong Kong Police say they have arrested three men in connection with the fire, which is still burning, on suspicion of manslaughter.
Meanwhile, firefighters say falling debris, including bamboo scaffolding surrounding the buildings, is making it difficult to extinguish the blaze — and it is still unknown how many people remain trapped inside.
Here's what we know.
What caused Hong Kong's Tai Po fires?
Authorities haven't said what started the fire, which sparked just before 3pm local time on Wednesday at Tai Po's Wang Fuk Court complex, but have established a taskforce to determine the cause.
The complex's eight high-rise buildings were covered in bamboo scaffolding and a green protective mesh because they were undergoing renovations.
Officials earlier said the fire started on the scaffolding, before spreading to the inside of the building and to nearby apartment blocks, likely fanned by strong winds.
While seven of the towers burned, police and firefighters were able to access the eighth building.
Security Secretary Chris Tang says they discovered "exterior netting, tarpaulin and plastic sheeting that burned far more intensely than permitted materials" as well as styrofoam stuck to window frames.
Fire Services Director Andy Yeung said the styrofoam panels were blocking ventilation gaps and were extremely flammable, prompting police to investigate whether criminal activity was involved.
He said the material would have caused the fire to spread more quickly within the blocks themselves, spreading from flat to flat through the corridors.
Who has been arrested?
Police have arrested three men, aged between 52 and 68, on suspicion of manslaughter over the fire.
They are two directors and an engineering consultant at a company that was carrying out maintenance work on the building, according to Eileen Chung, a senior superintendent of the Hong Kong Police Force.
"We have reason to believe that those in charge at the company were grossly negligent, which led to this accident and caused the fire to spread uncontrollably, resulting in major casualties," she said.
Is the fire still burning?
While the blaze in three of the affected towers is largely under control, small pockets of fire continue to burn in four other buildings.
The Hong Kong government said fire crews were still working through "extremely difficult conditions".
Firefighters are moving floor by floor and have so far reached the 17th to 18th floors in most towers.
Derek Armstrong Chan, the deputy director of fire service operations, earlier said the temperature at the scene was very high.
"There are some floors where we have been unable to reach people who requested help, but we will keep trying," he said.
Where is the fire?
The blaze is centred on Wang Fuk Court, a cluster of apartment towers in Tai Po, a district in Hong Kong’s north-east near the mainland border on the southern edge of the Pearl River Delta.
Here is a map of the fire's location:
[MAP: tai po]Why does Hong Kong use bamboo scaffolding?
Hong Kong is one of the last places in the world to use bamboo scaffolding in modern construction.
It stems from ancient techniques that originated in China and other parts of Asia.
While government regulations in China phased out its use in the 1990s, it is still popular in Hong Kong.
Bamboo poles are cut to size and then held together with nylon ties in structures that climb high in the urban landscape.
Industry estimates from January this year said that about 80 per cent of major construction and renovation projects in Hong Kong used bamboo scaffolding.
The remaining 20 per cent used metal and other materials.
Bamboo is lightweight, easily customisable, and relatively cheap compared to steel.
However it can burn, break down and become weaker in rain, which has raised some safety concerns.
Is bamboo scaffolding safe?
In March, local media reported that 23 people had died in industrial accidents involving bamboo scaffolding since 2018 in Hong Kong.
Earlier this year, the government's development bureau announced a plan to use more metal in scaffolding in public building works.
An internal memo noted that bamboo scaffolds had "intrinsic weaknesses such as variation in mechanical properties, deterioration over time and high combustibility, etc, giving rise to safety concerns".
The bureau wanted 50 per cent of all new building projects to use steel from March onward this year.
However, not everyone was pleased.
Some labour unions said the move would impact some 4,000 scaffolders and called instead for better training and site management.
Hong Kong's so-called "spidermen" are trained to construct bamboo scaffolding.
Chairman of the Hong Kong and Kowloon Bamboo Scaffolding Workers Union, Ho Ping-Tak, told CNN it was an art form.
"Sometimes people spend one, two, three or even four years learning bamboo scaffolding and may not become masters," he said.
"But with metal, the technical requirements are lower. If you have the strength, you can generally meet the requirements in a much shorter time."
While discussion of bamboo scaffolds often focuses on its use in urban construction, it continues to be used in cultural and religious festivals.
A scaffold structure was included in Hong Kong's pavilion at the Venice Biennale this year — something that organisers said was decided before the government's announcement.
It has also been used to make temporary theatres and performance spaces.
ABC/wires
