Officers from the Metropolitan Police were called to Tillett Close by London Fire Brigade colleagues at 1.22am yesterday (May 24).
A mother and her three children were killed and have been named by the polive.
A 13-year-old girl is fighting for her life in the hospital, and a woman in her 70s was also taken, but has been released.
A 41-year-old man was arrested at the scene in connection to the incident.
He remained in custody but has since been bailed and detained under the Mental Health Act.
Superintendent Steve Allen, from the Met’s local policing team in north-west London, said: “Our thoughts go out to all those impacted by what has happened.
“Specialist officers are continuing to support the wider family who have asked for privacy at this deeply upsetting time.
“Local officers are working closely with officers from the Specialist Crime Command on what continues to be a very complex investigation.
“I’d like to thank the members of public, our first responding officers and colleagues from other emergency services for their efforts during this highly pressurised and distressing incident.
“Equally, we appreciate this has affected the wider community who have been extremely supportive. You will see extra officers in the area during the coming days and some of the cordons will remain in place.
“We are grateful for your patience and understanding. If you have any concerns then please speak to them.”
Anyone with information that could assist the Met with their investigation have been asked to call 101 giving the reference 509/24MAY.
Information can also be shared anonymously, with the independent charity Crimestoppers, by calling 0800 555 111.
