Investigators are examining how a blaze in London tower block was able to spread so quickly.
Doubts have been raised raised over whether escape routes and fire prevention measures were adequate at the 12-storey 1960s building, which had a single central staircase.
Fire officials said a 'unique situation' caused 'one of the most significant fires in some time'.
34-year-old Helen Udoaka and her three-week old daughter Michelle, were among those killed in the fire at Lakanal House in Camberwell, south London, last night.
Dayana Francisquini (26) and Filipe Francisquini aged three, also died, along with 31-year-old Catherine Hickman.
The sixth victim, who has not yet been identified, is believed to be a four-year-old girl.
A dozen people are still being treated in hospital, mostly for minor injuries.
The blaze in Havil Street began on the fourth floor and spread rapidly to the 11th floor, according to London Fire Brigade.
30 people were rescued and were evacuated from the building.
