Two teenage girls suspected of plotting an attack against a Parisian concert hall have been arrested and presented to an anti-terrorism judge.

The Paris prosecutors office confirmed in a message to the Associated Press that the girls, aged 17 and 15, were arrested on Wednesday by counter-terrorism agents as part of an investigation for criminal conspiracy in connection with a terrorist enterprise that had been opened a day before. BFMTV channel first reported the news.

Both girls are now facing preliminary charges of criminal association linked to terrorism, prosecutors said.

No details about where the teenagers live, their identities or where the arrests were made have been given.

Prosecutors said early investigations indicate the girls’ project appears to have still been in the thinking stage as no weapon or explosives were found. They have requested that the youngest girl be placed in temporary custody and the other under judicial control.

The arrests came nearly four months after the deadly attacks at the Bataclan concert hall and other locations in Paris, when 130 people were killed on 13 November.