Rep. Jason Chaffetz, chairman of the House Oversight Committee, said Wednesday night that material related to Hillary Clinton's private email use that was provided by the FBI is so highly classified that he does not have the security clearance to read most of it.

"The sensitivity of the material is such that even I, as the chairman of the Oversight Committee, the chief investigative body, I don't have the proper security clearance as a member of Congress to look at this," Chaffetz said on Fox News.

The Utah Republican said the FBI files, which include notes from witness interviews and other documents from the agency's year-long probe, could only be accessed in a secure facility known as an SCIF that was "under lock and key and guard." Once inside the SCIF, Chaffetz noted, the documents available were still heavily redacted.

"It goes to the nature of how this very sensitive material, material that put people's lives in danger, was out there in the open," he said.

Chaffetz dismissed Clinton's argument that her team was simply careless in its efforts to establish a private email network housed in the Democratic nominee's basement.

"It went on for years and she was fairly sophisticated," he said. "And yet they created this scheme in such a way that they could bypass this ... she set up the server on the very day she started her Senate confirmation."

Chaffetz also noted that the classified information that ended up in Clinton's inbox had to have been cribbed from a secure network and placed into a nonsecure setting deliberately. The question of who did that and why should have been at the heart of the FBI investigation, Republicans have said.

Congressional Democrats blasted the push to obtain the FBI's investigative files this week, likening the Oversight Committee review to the two-year probe of Benghazi that concluded this summer.