As pressure builds on Hillary Clinton to explain her official use of personal email while serving as secretary of state, she faced new complications Tuesday. It was disclosed her top aides are being drawn into a burgeoning federal inquiry and that two emails on her private account have been classified as “Top Secret.”

The inspector general for the Intelligence Community notified senior members of Congress that two of four classified emails discovered on the server Clinton maintained at her New York home contained material deemed to be in one of the highest security classifications – more sensitive than previously known.

The notice came as the State Department inspector general’s office acknowledged that it is reviewing the use of “personal communications hardware and software” by Clinton’s former top aides after requests from Congress.

“We will follow the facts wherever they lead, to include former aides and associates, as appropriate,” said Douglas Welty, a spokesman for the State Department’s inspector general.

Despite the acknowledgment, the State Department inspector general’s office has left numerous unanswered questions, including exactly who and what is being investigated. The office initially declined to comment and referred questions to the Intelligence Community inspector general’s office, which said it is not currently involved in any inquiry into aides and is being denied full access to aides’ emails by the State Department. Clinton, herself, is not a target.

The expanding inquiry threatens to further erode Clinton’s standing as the front-runner for the Democratic presidential nomination. Since her reliance on private email was revealed in March, polls in crucial swing states show that increasing numbers of voters say Clinton is not honest and trustworthy, in part, because of her use of private emails.

Sen. Chuck Grassley, the Republican chairman of the Judiciary Committee, wants Clinton and her aides to “come clean and cough up” information about their personal email use.

“Both the State Department and Intelligence Community inspectors general should be looking into the staff use of the Clinton private server for official State Department business. This means giving both inspectors general access and custody of all emails that haven’t already been deleted,” said Grassley of Iowa. “From what is publicly known, it appears that the investigation thus far has focused so much on the former secretary of state, that it’s gotten lost that high-level staff apparently also used this server too.”

State Department spokesman John Kirby referred to the Intelligence Community’s disclosure as a recommendation to “upgrade” the two emails’ classification to “Top Secret.” In a statement, he said that “while we work with the Director of National Intelligence to resolve whether, in fact, this material is actually classified, we are taking steps to ensure the information is protected and stored appropriately.”

At least four top aides have turned over records, including copies of work emails on personal accounts, to the State Department, which is collecting them in response to a subpoena from Capitol Hill, according to the department. Lawmakers have demanded records, including personal emails, from six other aides, but it’s unknown whether they used personal email for work.

Three Republican Senate committee chairmen _ Richard Burr of North Carolina, Bob Corker of Tennessee and Ron Johnson of Wisconsin _ requested in March that both inspector generals conduct an audit of aides’ personal emails.

“As outlined in the joint letter with his colleagues, Chairman Burr has expressed concern that State Department aides may have transmitted sensitive or classified information in an insecure manner,” Burr spokesman Becca Glover Watkins said. “Chairman Burr expects that the IGs will conduct their investigations as requested.”

But it’s not clear that’s being done.

Welty initially said the Intelligence Community inspector general, which had already been looking into the issue of whether classified information has been improperly shared with or by Clinton, has taken responsibility for deciding which emails to review, from whom and determining their classification.

However, Andrea Williams, a spokeswoman for the Intelligence Community Inspector General, said that office “never had access to any emails other than those provided to the State Department by former Secretary Clinton.”

But she said her office could get involved. “The intent is not to just focus on Clinton,” Williams said.

An impasse remains between the State Department and the Intelligence Community’s inspector general over whether the intelligence watchdog should be provided copies of emails due to jurisdictional issues. The State Department has provided records to its Inspector General. A State Department spokesman declined to comment on the issue.

Revelations that dozens of Clinton’s emails now include classified information has prompted an FBI inquiry into whether classified information was improperly stored on her private server and a thumb drive held by her attorney. The news has sparked fear among national security experts that the federal government’s secrets may have been exposed or even hacked. However, the two inspectors general said the material in Clinton’s email was not marked as classified at the time. The FBI declined to comment.

Clinton, which has repeatedly denied she ever sent or received classified information, hasattempted to downplay the scrutiny as mere partisan attacks, but questions about her judgment and motive for setting up a private server in her Chappaqua house in 2009 continue to dog her. Her campaign declined to comment.

The case is more complicated because of Clinton’s prominence. A former secretary of state, senator and first lady, Clinton has friends and connections throughout the administration and on Capitol Hill.

“I think the headline is that there’s nothing but murkiness and non-answers from the State Department,” said Bradley Moss, a lawyer who is representing Gawker, a media organization suing for access to one aide’s emails. “I think the State Department is figuring this out as it goes along, which is exactly why no one should be using personal email to conduct government business.”

In March, the House committee investigating the fatal attacks in Benghazi, Libya, in 2012subpoenaed records, including personal emails relating to official business, from 10 Clinton aides at the State Department about Libya for a two-year period. In turn, the department asked them for records.

Administration officials and Clinton aides have declined to provide a full list of which aides used personal email for government business or who might have had an email account on Clinton’s personal server.

Clinton acknowledged that Huma Abedin, her deputy chief of staff and one of Clinton’s closest confidants, had an account on her personal server in a sworn affidavit filed Monday in a Freedom of Information lawsuit seeking State Department records.

Clinton’s affidavit was her first disclosure that any of her former aides used personal accounts or accounts on her personal server to conduct business. Clinton said that her chief of staff, Cheryl Mills, did not have an account on the server.

Mills, Jake Sullivan, also a deputy chief of staff, and Deputy Assistant Secretary of State Philippe Reines have turned over records to the State Department, including personal emails, in response to a subpoena by the House committee investigating the fatal attacks in Benghazi, Libya in 2012, according to the State Department.

Mills had planned to delete her emails after submitting them to the State Department, according to an Aug. 6 letter from her attorney to the State Department submitted as evidence in the Freedom of Information suit by Judicial Watch, a conservative public interest group that also has sued the State Department seeking Clinton aides’ emails. Her attorneys planned to keep a copy.

But U.S. District Court Judge Emmet Sullivan, who is presiding over the suit, issued an order Friday instructing the State Department to direct Clinton, Mills and Abedin not to destroy any records.

Reines and Sullivan did not respond to messages nor did attorneys for Mills and Abedin.

Clinton has turned over 30,490 work emails to the State Department in response to a request from the agency, but said that she deleted another 31,830 personal emails.

But in June, after Clinton’s longtime confidant Sidney Blumenthal gave the House committee emails between him and the former secretary of state, the State Department realized it was missing all or part of 15 emails.

The Intelligence Community’s inspector general requested that the FBI scrutinize the security implications of Clinton’s use of the private email after determining that at least five emails containing classified information had been stored on her private server, including one email that State Department officials inadvertently released in response to a public records lawsuit. Two others are under review for final classification.

I. Charles McCullough III, the inspector general for the intelligence community, said State Department officials had warned that there were “potentially hundreds of classified emails” on Clinton’s private server.

The State Department has begun to release Clinton’s emails in response to a public records lawsuit. Clinton said that the use of personal email by State Department employees was permitted at the time, but State Department and White House officials decline to say whether she sought or received prior approval from anyone or whether anyone objected to it later.

The National Archives’ regulations permit the use of personal email for government business, but mandates that records must be kept.