The 16-year-old Isabella from Celle, who has been missing for around two weeks, is probably in France, according to the police.
Surprisingly, a call on Facebook led to a very specific hint, the police said on Tuesday evening in Celle.
A girl found in France was "with a probability bordering on certainty" to Isabella.
The exact circumstances of their disappearance are still unclear - it will be further investigated.
The police have so far assumed a violent crime.
A special commission evaluated contacts between young people in chat groups and in social networks.
On Easter Monday, the officials once again urgently asked the population for help.
The girl with the nickname Isi had reportedly left her parents' home unnoticed on the morning of March 22nd.
The young person did not take any keys, wallet or cell phone with her.
Therefore, the police assumed that they wanted to meet someone near the house.
There is no reason to believe that Isabella wanted to run away, it was said last.
The parents called the police on the same day.
mjm / dpa