The incident happened late on Sunday evening
She claimed a man assaulted her in Collier Row Road shortly before 11pm on Sunday, 9 August.
The girl is being supported by officers, and detectives from the East Area Command Unit are investigating the report.
Police say no arrests have been made.
Witnesses, or anyone with information about the incident, are asked to contact police on 101, quoting CAD 9459/09AUG.
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Tags: Romford, Havering, Collier Row