A pathologist could find no formal cause of death for two young children whose mother was arrested on suspicion of their murder, police said tonight.
The 10-week-old boy and his 14-month-old sister, Lily Sky Boots, were found unconscious on Wednesday evening by their father, Jeff Boots, when he returned home from work, sources said.
Officers from the Metropolitan Police arrested their mother, Felicia, at the semi-detached home in south-west London after emergency services were unable to revive the children at the scene.
Tonight, Scotland Yard said the arrested woman remained in custody.
A spokesman said: "Post-mortem examinations took place today at Great Ormond Street Hospital - no formal cause of death was given, we await the outcome of further tests.
"Next of kin are aware.
"Though we are satisfied as to the identity of the children, we do still await formal identification.
"Detectives from the child abuse investigation command are leading the investigation, and inquiries continue into the full circumstances of the incident.
"The deaths are being treated as murder."
Detectives suspect Mrs Boots smothered the children while suffering from post-natal depression.
The deaths happened just days after the family moved into their £1.2 million home.
Mrs Boots, who is in her 30s and is a trained hairdresser, had been busy completing removal from a nearby penthouse apartment in the weeks before the deaths.
Both Mr Boots, an investment banker, and his wife are understood to have moved to the UK in the last few years from Canada.
Neighbours of the couple's new three-storey home, which boasts a 45ft back garden near Wandsworth Common, said the family seemed "very nice".
Locals also confirmed that the couple featured in pictures on Facebook showing them smiling together under an umbrella.
Jackie Cook, 52, said it was too early to have known the couple well.
She said: "It's such a tragedy, I can't believe it. Last night there were police swarming everywhere. There were ambulances and police cars all along the road.
"I think they only moved a couple of weeks ago."
The woman, unofficially named as Felicia Boots, has been arrested on suspicion of killing her children. Credit: Supplied
The estate agents described the house as "beautifully presented" Credit: Savills