Two of Hillary Clinton's top aides may have received legal protection for their destruction of emails, Rep. Darrell Issa, R-Calif., said Wednesday.

Heather Samuelson and Cheryl Mills, two former State Department officials who also served as Clinton's attorneys, both secured immunity agreements during the year-long investigation of Clinton's private email use.

Comey described their deals as "use immunity" covering only the information that was contained on laptops sought by investigators.

But Issa said the agreements provided "transactional immunity," which could have shielded them from prosecution if they deleted key emails.

"I read them," Issa said of the immunity deals, noting the FBI had not allowed lawmakers to remove copies of the agreements from the SCIF where they are stored. "You gave immunity from destruction to both of those attorneys."

"I'm pretty sure that what was granted was use immunity ... which means no statement can be made against you directly or indirectly," Comey said.

During the hearing Wednesday before the House Judiciary Committee, lawmakers pressed Comey on why Bryan Pagliano, a former IT aide to Clinton, received two immunity deals.

The FBI director explained that one was a "queen for a day" agreement covering what Pagliano said in an initial interview, and noted that the first agreement was an "intermediate step" that paved the way for the second agreement.

Republicans on the Judiciary Committee grilled Comey on the lingering uncertainties surrounding Clinton's email probe, including whether aides destroyed emails and devices before or during the criminal investigation.

"We uncovered no evidence that devices were destroyed during the pendency of our investigation," Comey said.

The FBI director faced intense scrutiny of the immunity agreements provided to at least five witnesses connected to Clinton.

"Our job is to tell [the Justice Department] what facts we'd like to get access to, the prosecutor's job is to figure out how to do that," Comey said, noting he thought the five immunity agreements known to the public were the extent of the protections provided during the probe.

Comey said FBI officials would be in "big trouble" if they were caught engaging in the same conduct as Clinton, but noted they would not face prosecution.