The police took the Swedish climate activist Greta Thunberg into custody along with a group of other demonstrators during a protest near the town of Lützerath.
"The group is in police custody for identity verification," said the spokeswoman for the Aachen police headquarters, Dana Zimmermann, on Tuesday evening at the request of the AFP news agency, without naming Thunberg.
There had previously been reports from climate activists that Thunberg had been arrested.
According to the police, the number of people taken into custody is “in the middle double-digit range”.
These would have to remain in police custody until everyone's identity had been established.
If some did not want this, "then everyone will have to wait," said Zimmermann.
However, it is not an arrest in the legal sense.
The group therefore took part in another rally against the evacuation of Lützerath and the brown coal opencast mine in the region.
Some, including the group taken into custody, "broke away from the demonstration" and "ran towards the demolition edge of the opencast mine".
According to the police, what will happen to them next will be “decided when the identity check is complete”.
Pictures on social networks showed how several police officers carried Thunberg away.
The All Villages Remain initiative wrote about an arrest of the Swedish climate activist on Twitter, which thanked Thunberg for her support.