The investigation has also found that the girl's acquaintance was in possession of her belongings.
No evidence of a sexual offense or any sexual contact with the girl has been found, the spokesperson said.
The girl went missing for 30 hours, with reports suggesting she had been kidnapped and raped by a group of migrant men.
Almost immediately following news of the incident being circulated in Russian-language media, Berlin police said there was no evidence of sexual assault.
With tensions high after the reports of hundreds of assaults on women in Cologne at New Year's Eve, hundreds of Russian-speaking Germans protested last week over what they believed to be a police cover-up of the case.