The causes of the devastating fire that killed at least 55 people in Hong Kong. Experts have a major suspect, possibly responsible for spreading the fire

Authorities say they have reason to believe that those responsible at the company renovating the five skyscrapers “exhibited gross negligence” in their work. Experts believe that the bamboo scaffolding – and other flammable materials used – contributed to the rapid spread of the fire, write the South China Morning Post and CNN.

The devastating fire that engulfed a residential complex in Hong Kong spread in an “unusual” way and authorities have opened a criminal investigation, Hong Kong Security Secretary Chris Tang said Thursday, according to public broadcaster RTHK, CNN quoted.

Three men were arrested on suspicion of manslaughter in connection with the tragedy – two directors and a consultant of a construction company renovating the apartment blocks.

Renovation work began last July and the blocks were covered in scaffolding and netting, according to the South China Morning Post, a Hong Kong daily.

“We have reason to believe that the responsible persons in the company showed gross negligence, which led to this accident and caused the fire to spread uncontrollably, resulting in a large number of casualties,” Eileen Chung, a Hong Kong police commissioner, said on Thursday.

Chung did not name the company, but later on Thursday police raided Prestige Construction and Engineering Company's premises. According to local media, the police seized boxes of documents as evidence.

Authorities are also investigating “possible acts of corruption” related to renovations at Wang Fuk Court, the complex affected by Wednesday's fire.

The Independent Anti-Corruption Commission, Hong Kong's official anti-corruption body, announced on Thursday that it had set up a special team “given the significant public interest in this matter”.

The number of people who died in the fire rose to at least 55, the city's fire department announced Thursday. At least 123 people were injured in the fire, including eight firefighters.

Fire officials did not immediately provide an update on the number of people who remain missing after the fire. Officials had previously said 279 people were missing.

Flammable materials

The exact cause of the fire has not yet been determined. The South China Morning Post wrote that authorities are considering a theory that the fire may have started from a worker's cigarette – but nothing has been confirmed.

Authorities still have several unanswered questions. It remains unclear why the tower blocks were not evacuated sooner once the fire began to spread from the first building, writes CNN.

However, the authorities consider the possibility that flammable materials, including the polystyrene plates that blocked the windows of several apartments, may have contributed to the spread of the fire.

Officials said they suspect other construction materials found in the apartments — including safety netting, canvas and plastic sheeting — did not meet safety standards.

“These polystyrene boards are extremely flammable and the fire spread very quickly,” fire services director Andy Yeung said Thursday.

“Their presence was unusual, so we notified the police for further investigation.

The city's housing authorities will check whether the protective layers used to cover residential buildings during renovation were sufficiently fire-resistant, according to Hong Kong leader John Lee.

Bamboo scaffolding, in the spotlight

To blame for the rapid spread of the fire seems to be especially the bamboo scaffolding that covered the buildings, a traditional construction material that the authorities are still gradually removing for safety reasons, writes The Guardian.

Gary Au Gar-hoe, a spokesman for the fire protection engineering division of the Hong Kong Institute of Engineers, explained to the South China Morning Post that the bamboo scaffolding can catch fire even with a layer of fire-retardant material applied to its mesh, while the heat radiated from one of the buildings could have ignited the scaffolding and surrounding buildings.

Hong Kong is one of the last places in the world where bamboo is widely used in construction.

Bamboo is valued for being lighter and cheaper than metal alternatives. Its use in construction is also considered an art form in itself, with bamboo towers depicted in paintings dating back to the Han Dynasty 2,000 years ago.

In March, the government announced it would begin phasing out the use of bamboo in favor of fire-resistant steel for safety reasons.

The authorities said that 50% of public construction works will have to use metal frames.

But the Hong Kong and Kowloon Bamboo Scaffolding Workers Union has previously spoken out against giving up bamboo.