French investigators opened preliminary proceedings against three new suspects for membership of a terrorist group, sources close to judicial circles said on Friday, three weeks after the brutal beheading of a history teacher by a suspected Islamist. Two adults are in pretrial custody and one minor is under judicial supervision, the sources said. The three suspects are two 18-year-old men and one 17-year-old, it was reported. One or more of the suspects reportedly had contact with the attacker. The suspected terrorist, an 18-year-old of Russian-Chechen origin, was later shot dead by security forces. Teacher Samuel Paty was murdered on October 16 in a crime that shocked France and led President Emmanuel Macron to intensify a planned crackdown on Islamist activism. Paty was killed apparently for discussing controversial caricatures of the Muslim Prophet Mohammed that originally appeared in satirical magazine Charlie Hebdo , in a class on freedom of expression. Investigators are treating the crime as an act of terror motivated by Islamist extremism. Soon after the crime, investigators sought charges against seven people, six of whom were accused of complicity in a terrorist murder.