Veronica Panarello, 25, was questioned for six hours overnight by police in Santa Croce Camerina, south-east Sicily.
She is accused of murdering her son, Andrea Loris Stival, on November 29th and dumping his body in a canal, Ansa said.
His body was found later that day and a murder investigation launched. Early reports said that the boy suffered a head wound and may have been sexually abused, although coroners have since revealed he was strangled with a cable tie.
When two teachers visited the family home on Monday, Panarello allegedly tried to give them a pack of cable ties and told them her son had said they were needed at school. The teachers deny making such a request, Ansa reported.
Panarello denies murder and will face further questioning onTuesday.
She maintains that she drove her son to school the morning he went missing. CCTV footage, however, appears to show the boy returning home and his mother later driving towards the Mulino Vecchio area where his body was found, Ansa said.
“She is being investigated but is not guilty,” said her lawyer, Francesco Villardita.
Investigators have 48 hours to question Panarello and bring charges against her, before they must appeal to a judge for more time.