A police spokesperson said the girl’s next of kin have been made aware and are being supported by officers.
London Ambulance Service was called at a similar time to police after receiving a report of a person in the water at Lowestoft Mews, close to the airport.
"We sent resources to the scene, including an ambulance crew, an advanced paramedic, an incident response officer and members of our hazardous area response team," a spokesperson said.
"Our crews assisted our emergency services partners at the scene but were later stood down."
London Fire Brigade deputy assistant commissioner Joseph Kenny said: "Firefighters responded to reports of a person in the River Thames near Lowestoft Mews, Newham.
"Crews from East Ham, Barking, Ilford and Bexley fire stations were sent to the scene alongside crews from the HM Coastguard, RNLI, London Ambulance Service and the Metropolitan Police Service.
"The brigade also deployed its drone team and fire boat as part of its response, with crews carrying out a systematic search of the area.
"The brigade was first called about the incident at 13:23. Search operations for firefighters were concluded at 15:49 when responsibility for the incident was left with the police."
A spokesperson for the RNLI said: "Tower RNLI was requested to launch this afternoon (March 31) to an incident near Woolwich.