Officers were called at 4.12pm on Saturday, 11 December following a report that a child was unresponsive at a flat in Sutton Street, E1.
She was taken to an east London hospital where she was sadly pronounced dead later the same day.
Formal identification is yet to take place but officers believe the deceased is Fatiha Sabrin. Her next of kin are aware and are being supported by specialist officers.
A special post-mortem examination will take place in due course.
Fatiha’s death is being treated as unexplained and is being investigated by detectives from the Met’s Specialist Crime Command.
A sweep of the building was carried out by the London Fire Brigade and a quantity of chemicals – believed to be used for pest control – were discovered. Work is underway to remove the chemicals from the property.
Detective Chief Superintendent Marcus Barnett, in charge of policing for Tower Hamlets and Hackney, said: “Our thoughts remain first and foremost with Fatiha and her family. This is a tragic incident and we are doing everything we can to support them at this time and to understand what has happened.
“All other residents in the building were evacuated as a precaution and we understand that it is very distressing for them to be away from their homes. We are working closely with the local authority to ensure residents’ needs are being met and to provide timely updates as to when they may be allowed back into their properties.”
A number of other people in the building received treatment after reporting feeling unwell. One woman and a child remain in hospital, their injuries are not believed to be life changing or life threatening.