The sources said the notification from the central government had been received and an FIR could be registered anytime soon.
Pradyuman, a Class 2 student, was found dead in a school toilet with his throat slit on September 8.
A school bus conductor was arrested the same day for allegedly killing the child.
Mr Thakur's lawyer alleged that the CBI inquiry had not yet started despite the Haryana government recommending it. "If the formal inquiry by the CBI is not started by tomorrow, then Barun Thakur will move the Supreme Court on Monday," he added.