Inaccessible rear staircases have been identified as the main reason for the high death toll in the Mong Kok inferno that claimed nine lives last November.
Seven of the 12 flats in two adjoining eight-storey buildings in Fa Yuen Street had their rear staircases blocked after the flats had been illegally subdivided into self-contained rooms, according to a government source.
"The exit to the rear staircase in these flats was blocked by one of the subdivided rooms and only occupants of the room could use it," the source said. "Other tenants were unable to access the exits and had to escape through the front door, but were caught by choking fumes that filled the front staircase.
"They inhaled smoke and passed out on the staircase. Some tried to run to the roof but were unable to make it."
A woman, who ran with her boyfriend in an effort to escape Hong Kong's deadliest fire in 15 years, was found dead near an exit to a roof. Her boyfriend survived but was in intensive care in hospital for days.
The source said results of postmortem examinations showed the nine victims, all found in the front staircase, died from suffocation.
After the blaze, in which another 34 people suffered injury, the Buildings Department issued seven orders to landlords to remove illegal building works.
Yesterday, a department spokeswoman said all the flats had been rectified and two owners had been fined by a court for failing to comply within the period stated in the removal order.
The Fire Services Department said its officers had conducted 11 checks in the two buildings since August 23 and spotted minor obstructions in fire escapes such as public corridors and staircases. It said the obstructions had been removed after the people responsible were traced.
As originally built, the buildings at 192 and 194 Fa Yuen Street have two flats on each floor, on either side of the joint staircase, with front and rear exits.
The blockages that caused the death trap will be described in the full report on the blaze, which is likely to be submitted to the Coroner's Court later this year.
A police source said the report would include statements taken from hundreds of people, including survivors and rescuers, and contain opinions from a variety of independent and government experts.
Recommendations to improve the fire safety of old buildings are expected to be included.
Police are compiling the report after analysing information from the Fire Services, Buildings and Electrical and Mechanical Services departments.
The other factor contributing to the death toll was the rapid spread of the flames that filled the front staircase with dense smoke.
The fire, believed to have been started by a faulty electrical cable, broke out in a market stall selling children's clothes near the front staircase early on November 30.
After the stall burst into flames, the fire spread to the mezzanine-floor flats of the two blocks through canvas awnings.
The South China Morning Post visited Fa Yuen Street yesterday and found that the buildings around where the fire broke still had subdivided flats, but stairwells were clear. The subdivision of flats was indicated by doorbells with four buttons labelled A,B,C and D.
A real estate agent said that the rent for a subdivided flat was HK$3,000 for a 100 sq ft space with private bathroom.
Additional reporting by Jennifer Cheng