Washington (CNN) Colin Powell and top staffers for Condoleezza Rice received classified information through personal email accounts, according to a new report from State Department investigators.

Hillary Clinton has received severe criticism -- particularly from Republicans and computer security experts -- for using her personal email account while serving as the nation's top diplomat under President Barack Obama. Thursday's revelation about the two secretaries of state under former President George W. Bush gave her supporters an opportunity to claim the Democratic presidential candidate was being singled out over the practice.

The emails were discovered during a State Department review of the email practices of the past five secretaries of state. It found that Powell received two emails that were classified and that the "immediate staff" working for Rice received 10 emails that were classified.

The information was deemed either "secret" or "confidential," according to the report.

"Based on the department's responses and findings to date, additional potential classified material and/or highly sensitive information not intended for distribution may reside in the Department's unclassified paper and electronic archives associated with Secretaries Powell and Rice and their respective staff," a memo about the report said

In all the cases, however -- as well as Clinton's -- the information was not marked "classified" at the time the emails were sent, according to State Department investigators.

Powell noted that point in a statement on Thursday.

"The State Department cannot now say they were classified then because they weren't," Powell said. "If the Department wishes to say a dozen years later they should have been classified that is an opinion of the Department that I do not share."

"I have reviewed the messages and I do not see what makes them classified," Powell said.

Clinton has argued that the messages from her email have since been deemed classified by the intelligence community as part of an " inter-agency dispute " between the intelligence community and the State Department over whether the information should have been classified.

Additionally, Powell said he never kept the emails in his possession when he left the State Department. Unlike Clinton, Powell's emails remained in government computer servers.

An aide to Rice, who now teaches at Stanford University, said that Rice herself never used email -- not even a personal email account -- during her tenure.

Clinton, who is now running for president, has weathered a year of political fire for setting up a personal email server at her home in Chappaqua, New York to conduct business as secretary of state. That allowed her to place her official state communication outside government purview and under her complete control. Critics claim this put national secrets at risk.

John Podesta, Clinton's presidential campaign chairman, said these issues are overblown. All of these instances are examples of how government bureaucrats keep too many things secret, he said.

"Clinton agrees with her predecessor that his emails, like hers, are being inappropriately subjected to over-classification," he said in a statement.

Democrats blast probe

The inspector general's report was addressed to Patrick Kennedy, the under secretary of state for management. Kennedy was interviewed by the House Select Committee on Benghazi on Wednesday, and this report was also shared members of the government's intelligence community.

Rep. Elijah E. Cummings, D-Maryland, was the first to make these findings public. On Wednesday, he issued a statement blasting Republicans for singling out Clinton over the issue.

"Based on this new revelation, it is clear that the Republican investigations are nothing more than a transparent political attempt to use taxpayer funds to target the Democratic candidate for President," Cummings said.

There's now an effort to relax the investigation. House Speaker Paul Ryan and other top Republican politicians are wary of multiple congressional probes into Clinton's email appearing too political, and have instructed House chairmen to stand down and let the FBI take the lead.

"We are going to respect the FBI's investigation," Ryan told reporters on Thursday, adding that FBI Director James Comey and his team "have the tools they need to do it."

Ryan's remarks also came after House Oversight Committee Chairman Jason Chaffetz publicly touted his own review and suggested he had new information. Chaffetz's panel had already sent a letter to the State Department last month asking Secretary John Kerry for information about the department's handling of requests made under the Freedom of Information Act.

Chaffetz's efforts keep raising alarm bells inside Republican Party. Speaking about Clinton, he recently said: "I'm not specifically trying to target the secretary, but when she creates her own private email system, she's ensnarled herself."

Meanwhile, Ryan and other members of his leadership team are telling Chaffetz to back off, according to multiple House Republican sources. They're worried that Chaffetz, a Republican from Utah, will damage any credibility of an congressional inquiry by appearing overly partisan. Chaffetz has endorsed Florida GOP Sen. Marco Rubio for president and has gone on the campaign trail to boost his candidacy.

Similarly, the House Science Committee Chairman Lamar Smith has expressed interest in examining Clinton's use of a private server. But an aide to the House Science Committee now tells CNN they would "defer to the FBI's expanding investigation."

"We expect the FBI to do its job and fully investigate cybervulnerabilities that may have resulted from former Secretary Clinton's decision to deviate from established cybersecurity standards and requirements," the aide said.

Correction: The headline of this post has been updated to reflect that Rice's staffers received the emails that are now considered classified.