The FBI never asked top aides to Hillary Clinton to turn over all their electronic devices in the agency's email probe, eventually obtaining two laptops from the former secretary of state's attorneys, according to news reports.

"No one was asked for devices by the FBI," a source told Politico.

The omission left the FBI with having to rely partially on what was turned over to the agency by attorneys for the aides in their investigation of Clinton's private email server use.

Those documents were turned over to the State Department in response to the FBI's request last year, Politico reports.

But Republicans slammed the revelation, raising questions on the effectiveness of the inquiry.

"The more we learn about the FBI’s initial investigation into Secretary Clinton’s unauthorized use of a private email server, the more questions we have about the thoroughness of the investigation and the administration’s conclusion to not prosecute her for mishandling classified information," House Judiciary Committee Chairman Bob Goodlatte of Virginia told Politico.

On Monday, Senate Judiciary Committee Chairman Chuck Grassley of Iowa complained that the FBI might have not used traditional investigative methods in its inquiry.

"If the FBI is denied the ability to gather evidence through compulsory means, Secretary Clinton and her aides have enormous leverage to negotiate extraordinary concessions in exchange for voluntary cooperation," Grassley wrote FBI Director James Comey in a letter. "It is critical for the public to know whether the FBI has requested from the Justice Department vital investigative tools such as grand jury subpoenas and search warrants and whether it has been denied access to them."

Longtime Clinton aide Huma Abedin testified in June that she had turned over "all the devices" with State Department emails to agency officials.

Comey's decision to reinvestigate Clinton resulted from discovering tens-of-thousands of emails from Clinton's private server on a laptop shared by Abedin and her estranged husband, former New York Rep. Anthony Weiner.

A FBI spokesman Tuesday declined to explain specifically why the agency did not seek to obtain all relevant devices used by Clinton's aides, Politico reports.