Development of the fire
It appears that the fire fighters used the stairs to reach
the 21st Floor. Nothing has been said of their efforts to
connect to the dry riser system or its effectiveness in
relaying water to the 21st Floor (about 75m above ground).
By the time the firemen intervened, fire fighters were not
able to control the fire from the inside. By 01:00 they
had retreated and adopted a defensive mode; wetting down
the facades of adjacent buildings to avoid fire spread.
By about 01:15 the fire had spread to most of the floors
above the 21st Floor, resulting in a 10-storey blaze. Soon
afterwards the first chunks of facade started falling off,
taking the perimeter bay of the RC slab with it in places.
The spread of fire downwards was gradual at first, probably
due to burning embers dropping through services penetrations,
through slab edge openings and through other openings in
the concrete slabs caused by core wall expansion.
The fire led to the collapse of virtually all the slab
edge bay above 17th Floor as well as one internal bay on
the north side. The transition floor resisted the impact
of the partial collapses. Below this level there was substantial
structural damage and deformation, but no significant collapse.