A photo of murdered French teacher Samuel Paty was found in a search of the home of an 18-year-old woman, identified as the main suspect in an earlier possible Islamist attack plot in Beziers, the anti-terrorism prosecutor's office said.
French prosecutors had earlier arrested five women in the southern city of Beziers and launched a preliminary investigation in connection with the possible Islamist attack plot.
The beheading of Paty last October horrified France and led to renewed fears over Islamist attacks in the country.
The prosecutor's office added that the 18-year-old, whom they did not name, was unknown to security services. The search of her home also found notes referring to Islamic State, Nazi symbols and a plan of a nearby church.
Paty was killed by a Chechen teenager who was subsequently shot dead by police. The teenager wanted to avenge Paty's use of cartoons mocking the Prophet Mohammad during a class on freedom of expression. Muslims see any depiction of the Prophet as blasphemous.