The Justice Department is looking into John Bolton's book.
It opened a criminal investigation into whether Bolton — President Donald Trump's former national security adviser — shared classified information.
The New York Times reports a federal grand jury has subpoenaed records from Simon & Schuster — the company that published Bolton's book.
The DOJ previously tried to stop the book from being published. It was released in June.
Bolton's lawyer said Bolton "rejects any claim that he acted improperly, let alone criminally, in connection with the publication of his book." Bolton will cooperate with the investigation.