Four schoolchildren were being held by French police on Monday on suspicion of helping a man who beheaded a history teacher to identify his victim in return for money, a judiciary source said.
They were among 15 people being held over the incident, one of whom was previously convicted for terror-related crimes and admitted to having had contact with the man who killed Samuel Paty for showing a cartoon of the Prophet Mohammed to his class, the source said.
Paty was "pointed out" to his attacker "by one or more pupils, probably in return for payment", according to the source.
The killer's parents, grandfather and younger brother, detained over the weekend, remain in custody.
Those in custody also included a known Islamist radical as well as the father of one of Paty's pupils who had launched an online campaign against the teacher.
One other person was being held on suspicion of driving the killer, and another for allegedly accompanying him during the purchase of one of his weapons.