Former CIA Director David Petraeus hid materials in insulation in his attic as the FBI pursued its case about his mishandling of classified information, the bureau’s director, James Comey, said Thursday.

Comey made the disclosure to argue the point that the prosecution of Petraeus, who knew he had top secret information and lied to the FBI about it, differed from the investigation into Hillary Clinton’s handling of classified information.

Comey did not recommend charges against Clinton, the presumptive Democratic candidate for president, over her personal email server while she was secretary of State. He said his team found no evidence that she lied under oath or broke the law by discussing classified information in an unclassified setting.

In contrast, Petraeus pleaded guilty last year to knowingly sharing binders of classified information with his biographer, a woman with whom he was having a sexual relationship. The Justice Department made clear that the retired Army general knew the material was top secret when he divulged it and had lied to the FBI about it.