Secretary for Labour and Welfare Chris Sun Yuk-han said the government would investigate the accident and hold those responsible to account.

“We preliminarily suspect the base of the crane had obvious faults,” Sun said after visiting the Housing Society site in the afternoon.

He said the contractor had suspended the use of two other cranes on the site – where work started in June – until they were found to be safe.

Chief Executive John Lee Ka-chiu said the Labour Department had started an investigation into the accident, and would also inspect cranes across construction sites in the city to make sure they were safe. Families of the deceased and injured would be provided with economic support and counselling.

The Housing Society said it extended its deepest condolences and would provide a lump sum of HK$300,000 (US$38,000) to the families of each deceased worker, and HK$100,000 to those injured.

It was following up with the main contractor, Aggressive Construction Company, and would offer its full assistance to the government’s probe.

The contractor said it would assist the investigation and provide help to victims’ families.

According to the Fire Services Department, the crane was operating without a load on its 30m (98-foot) horizontal working arm at the time of the accident.

The crane collapsed at 10.49am, crashing down on several containers on the site. Five of the nine workers involved were inside the containers and trapped. Firefighters freed the five in 34 minutes, with one certified dead at the scene. He suffered a skull fracture and had been bleeding heavily.

The sixth worker, who suffered minor injuries, was trapped in the toppled crane’s cabin and rescued by firefighters. Two of the injured men had managed to climb out of the area before the arrival of emergency personnel.

The other victim was pulled from a crushed container and had suffered numerous bone fractures and was not breathing. He was certified dead at nearby United Christian Hospital.

The department deployed 15 fire engines and nine ambulances.

The six injured men, aged between 24 and 64, were taken to Queen Elizabeth and United Christian hospitals where two were in serious condition and four later discharged.

An employee surnamed Lam said he only realised the severity of the situation after hearing an order to suspend work following the accident, which he did not witness as he was indoors.

“I heard a sudden loud bang and I thought maybe it was just some bamboo scaffolding or wood that had fallen over,” Lam said.

He said work had not been rushed on the site.

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The grieving mother of the 22-year-old killed on the site broke down at United Christian Hospital. “I want my son back … Give me back my son,” she cried, as others comforted her as she left the hospital.

According to the Association for the Rights of Industrial Accident Victims, the 22-year-old was an engineering assistant.

The third man certified dead was a 25-year-old engineer surnamed Tsui, the association said. Association chief Fay Siu sin-man, who accompanied Tsui’s parents and relatives, said the victim was hard to recognise as a result of his facial injuries.

“His family hopes the company involved can pay attention to safety issues and conduct a review. They hope there won’t be another accident,” Siu said.

The Anderson Road Development is a major new housing area in Kowloon East. According to official documents, about 1,400 subsidised flats will be built on the accident site for a population of 4,000, with a 2025 completion date.

Along with six other public housing projects in the area, the construction will create about 6,710 homes, which are scheduled to be completed in stages between 2024 and 2026.

Professor Joseph Duncan Chi Wuh-jian, chairman of the Hong Kong Institution of Engineers’ safety specialist committee, said such incidents were rare.

“It is strange to see that the welding of the crane’s base was torn apart. Normally, tower crane incidents are due to overloading. But the crane involved in the accident was not carrying any weight at that time,” Chi said.

He said only detailed investigation could tell the cause of the accident but workmanship problems in the welding process could be one of the causes.

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At the scene, a steel beam attached to the bottom of the crane base was disconnected from another one underneath. It was fixed to a massive concrete block on the ground to form a firm base structure.

Ngai Hok-yan, a structural engineer with 40 years of experience, said photos showed the steel beams were not firmly joined with welding or through bolts.

“It seems there was oversight,” Ngai said. “The contractor and the Housing Society should both have had engineers on the site to make sure the crane base was properly set up.”

Another engineer, Jason Poon Cheuk-hung, who monitors public works, said site photos suggested the welds used on the beam were too thin.

According to government figures, 3,109 industrial accidents and 23 fatalities were reported in the construction sector last year. There were 2,532 accidents and 18 deaths in 2020.

A tower crane fell at a redevelopment site of Hysan Development in Causeway Bay, in 2007, causing two deaths and five injuries.

Six workers were killed at the International Commerce Centre in West Kowloon in 2009 after a work platform they were on collapsed.

Developer Sun Hung Kai Properties, the developers, visited the site and announced that each of the families would be given a compassionate payment of HK$1 million.