As well as investigating the cause of the blaze, it will probe the two deaths, review the use of industrial buildings and assess the work procedures of the Fire Services Department.

Yau Wai-keung, assistant director of the Fire Services Department, said evidence was already being collected and would be later submitted to the Coroner’s Court.

The blaze started at the SC Storage mini-storage facility on Tuesday morning, and was upgraded to a fourth-alarm fire later in the day.

In Hong Kong, fires are rated on a scale of one to five depending on their severity.

Firefighters Thomas Cheung, 30 and Samuel Hui Chi-kit, 37, who were killed, have been hailed as heroes and prompted an outpouring of public support and sympathy.

Ten other firefighters were taken to hospital, some suffering from heat exhaustion, and later discharged.

Metal sheets separating the 200 storage cubicles on the third floor posed a serious challenge for firefighters, who had to tear them down in order to gain access to the units and battle the blaze.

All the cubicles had been entered by last night, and the flames on the fourth and fifth floors put out.

Although the source of the blaze has been located on the central area of the third floor, firefighters declined to explain in detail as to what they believe caused the blaze.

Crews were still at work last night hosing water at other floors in the building, in an attempt to keep temperatures down.

The men said they were tired but determined to see the fire finally extinguished.

“The heat is much better today when compared to the first two days ... I am really hoping this will end by the morning,” one said.

A total of 34 fire engines and 180 firefighters and ambulance crews were deployed at the site yesterday.

The structural safety of the building has also raised concern after the Buildings Department announced that concrete was peeling from the ceiling on the third floor.

The damaged area was said to measure five metres by three.

However the department sought to ease fears and stressed there was no risk of the building collapsing despite earlier warnings from engineers.

“The Buildings Department carried out an assessment in the morning. They found that part of the ceiling on the third floor had peeled off, but it was still safe for us to do our work inside,” Leung Kwun-hong, assistant director of the Fire Services Department, said.

“The Buildings Department suggested we stay away from that area.”

Secretary for Development Paul Chan Mo-po admitted yesterday that Hong Kong has never had specific regulations governing mini-storage facilities.

He said that another cross-department task force, headed by the Security Bureau, would study how to strengthen fire safety measures in such facilities.

Questions and answers

At 10.30 last night, the deadly Ngau Tau Kok storage facility blaze had been burning for four days, 11 hours and 31 minutes . Here’s what we know – and what we don’t – about the fire which claimed the lives of two firefighters.

What caused the fire?

An official cause is still to be established, but yesterday (Sat) firefighters pinpointed the seat of the blaze to the central area of the third floor of the Amoycan Industrial Centre. This will be a crucial piece of information as the authorities – who so far do not suspect arson but have not ruled out a criminal involvement – piece together the complex jigsaw of what happened.

What are the major challenge facing fire crews?

Two hundred mini-storage cubicles on the blazing third floor of the building are packed with, in many cases, unidentified and possibly toxic contents, making the firefighting job particularly hazardous. The cubicles are separated by metal sheets, which have had to be knocked down one by one before the blazing contents can be extinguished.

The human toll so far?

Firefighters Thomas Cheung, 30, and Samuel Hui Chi-kit, 37, have been killed. Ten other firefighters have been sent to the hospital. All have since been discharged. The cause of the deaths is not confirmed but it is known that a number of those injured fell victim to the searing heat inside the building.

Is the building’s superstructure safe after almost five days on fire?

Engineers have warned that the building could collapse and some have even called for a controlled demolition. However, government officials insist there is no risk of the building collapsing in the immediate future. Even so, concerns remain as sections of concrete have been seen peeling off on the worst-affected third floor of the building.

What has the government been doing as the tragedy unfolds?

The day after the fire broke out, Secretary for Security Lai Tung-kwok announced that there would be a three-pronged inquiry. First, a citywide inspection of all mini-storage facilities would be carried out. Second, the Security Bureau would lead a cross-departmental task force to look into how to strengthen fire safety standards in such facilities, and third, operators would be contacted to discuss fire safety standards.

What wider problems does the fire point to?

Most mini-storage facilities are located inside old industrial buildings. Such buildings completed before 1973 are not required to be fitted with automatic sprinkler systems. The Ngau Tau Kok building falls into that category as it was built in 1961.