French anti-terrorism police on Tuesday detained seven people suspected of having communicated via social media with the killer of a schoolteacher whose beheading last year reopened debate about France’s cherished rights of expression, a judicial official said.

The teacher, Samuel Paty, was killed Oct. 16 outside his Paris-region school after showing caricatures of the Prophet Muhammad during a class debate on free expression.

His killer, identified by authorities as Abdoullakh Anzorov, was later shot dead by police. Anzorov, an 18-year-old refugee of Chechen origin who had become radicalized, according to authorities, claimed responsibility for the slaying in a text found on his phone that was accompanied by a photograph of the teacher.

The seven people detained Tuesday in the Paris region, as well as in western France and in the cities of Lyon and Toulouse, are suspected contacts of Anzorov, said the judicial official. The official wasn’t authorized to publicly discuss details of the investigation and spoke on condition of anonymity.

The suspects can be held for initial questioning by anti-terrorism investigators for up to 96 hours.

A total of 14 people were already being formally investigated and face preliminary terrorism- and murder-related charges in the investigation. Of those, seven have not been granted bail.