Prosecutors in Marseille say they are investigating but add that there is no evidence the teacher was deliberately targeted.
A teacher in southern France has received a death threat containing a photo of Samuel Paty, prosecutors say.
Two French teachers in the region of Aix-en-Provence have been sent threatening letters, the public prosecutor's office said on Monday.
One of the letters contained an image of Paty, who was beheaded last year outside his Paris school by an 18-year-old Chechen refugee.
The suspect said the attack on the 47-year-old history and geography teacher was revenge for Paty showing his class cartoons of the Prophet Mohammed, during a lesson on freedom of expression.
"In September, a couple of teachers received a photo of Samuel Paty in the mail, followed by a letter threatening their lives," said Dominique Laurens, the Marseille prosecutor.
The matter is now being investigated by the regional division of France's public security directorate, she added.
"The investigation is ongoing and at this stage, there is no evidence to link these facts to a course given by one of the teachers," Laurens told AFP.
Meanwhile, a man has been held in custody since Monday for threatening to kill staff at a secondary school in Valence.
The man's son had received a warning after shouting "Allah Akbar" during a tribute to Samuel Paty, according to prosecutors.
The incident took place during a minute's silence on Friday at the school in southeast France.
The 11-year-old student "was asked to reflect on his behaviour" and "offered to apologise to his teacher and classmates," the Grenoble education authority said in a statement.
The boy's father is a 43-year-old man who is known to the authorities, the public prosecutor in Valence added.