Police were called by the London Ambulance Service to an address in Lansdowne Crescent shortly after 2.25pm on Monday October 29 following reports of an injured infant.
On arrival, officers found a two-year-old girl who was treated by paramedics and taken to a west London hospital. She was pronounced dead at 3.17pm.
A post-mortem at Great Ormond Street Hospital is scheduled to take place in due course.
The spokesman said a woman, believed to be the toddler's mother, was taken to hospital and treated for shock.
Officers from Kensington and Chelsea CID are investigating the incident. At this stage it is being treated as non-suspicious.
More top news
The first Blue Moon since 2012 will appear over the UK on Friday. The next won't be until 2018.
Other hate crimes against muslims and gay people have also risen.
Archie's mum was fed up with the balloon floating around her living room so suggested he let it go to see how far it could travel.