Hong Kong firefighters brought under control on Thursday a huge blaze in an apartment complex that killed at least 55 and left nearly 300 missing, while police said its cause could have been a “grossly negligent” construction firm using unsafe materials.

Rescuers battled intense heat and thick smoke for more than a day after the blaze erupted as they fought to reach residents feared trapped on the upper floors of the Wang Fuk Court housing complex in the northern district of Tai Po.

Responding to Hong Kong's deadliest fire in 77 years, its leader John Lee said the government would set up a HK$300 million ($38.6 million) fund to help residents.

The city's development bureau had also discussed gradually replacing bamboo scaffolding across the Asian financial hub with metal scaffolding as a safety measure.

The eight blocks of the tightly packed complex have 2,000 apartments home to more than 4,600 people in the financial hub struggling to overcome chronic shortages of affordable housing.

A distraught woman carrying her daughter's graduation photograph searched for her child outside a shelter, one of eight that authorities said house 900 residents.

"She and her father are still not out yet," sobbed the 52-year-old, who gave only her surname, Ng. "They didn’t have water to save our building."

POLICE INVESTIGATE CAUSE OF BLAZE

On Thursday, police officers searched the building maintenance company responsible for the housing estate, seizing documents that mentioned it, media said.

The government identified the registered contractor for the complex as Prestige Construction and Engineering Company Limited. Prestige did not answer repeated calls for comment.

Police seized bidding documents, a list of employees, 14 computers and three mobile phones during Thursday's raid of the Prestige office, the government added.

"We have reason to believe that the company’s responsible parties were grossly negligent, which led to this accident and caused the fire to spread uncontrollably, resulting in major casualties," said police superintendent Eileen Chung.

China's President Xi Jinping urged an "all-out effort" to extinguish the fire and minimise casualties and losses, state broadcaster CCTV said.

The fire poses a challenging test for Beijing's grip on the city it has transformed since the mass pro-democracy protests of 2019.

FLAMES LEAP FROM BUILDINGS

Video images from the scene showed flames leaping from at least two of the 32-storey towers sheathed in green construction mesh and bamboo scaffolding.

Authorities said they had doused the flames in four of seven affected blocks, with those in the rest brought under control.

"We bought in this building more than 20 years ago," said a 51-year-old resident surnamed Wan. "All of our belongings were in this building, and now that it has all burned like this, what’s left?"

Police said in addition to the protective mesh and plastic coverings of the buildings, which may fall short of fire standards, they found foam material sealing some windows on one unaffected building, and installed by a construction company engaged in year-long maintenance work.

Police have arrested two directors and an engineering consultant of the company on suspicion of manslaughter over the fire, Chung added.

The estate has been under renovation for a year at a cost of HK$330 million, with each unit contributing between HK$160,000 and HK$180,000, media said.

Hong Kong's corruption body said it had launched an investigation into suspected graft related to the renovation.

A firefighter was among the dead, while dozens in hospital were in critical condition, authorities said on Thursday. About 279 people have yet to be traced.

More than 1,200 firefighters are battling to control the flames, along with 304 fire engines and rescue vehicles.

SEARCHING FOR RELATIVES

Harry Cheung, 66, who has lived at Block Two in the complex for more than 40 years, said he heard a loud noise at about 2:45 pm (0645 GMT) on Wednesday and saw fire erupt in a nearby block.

An online app showed reports of missing persons submitted through a linked Google document that detailed residents of individual towers and rooms.

It includes descriptions such as "Mother-in-law in her 70s, missing" or "one boy and one girl" or "Rooftop: 33-year-old male."

One simply reads "27th floor, room 1: He is dead." Reuters could not independently verify the information on the app.

The fire has prompted comparisons to London's Grenfell Tower inferno that killed 72 people 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.

COMPANIES CONTRIBUTE FOR RELIEF

Chinese companies and groups that have announced donations to the fire victims include automakers Xiaomi, Xpeng and Geely, as well as the charity foundation of Alibaba's founder Jack Ma.

Sky-high property prices have long fuelled social discontent in Hong Kong, where the fire tragedy could stoke further 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 world's most densely populated cities. Tai Po, near the border with mainland China, is an established suburban district home to about 300,000.

Occupied since 1983, the complex is under the government's subsidised home ownership scheme, according to property agency websites, a lifeline for the city's middle-income families.