The U.S. Justice Department has been asked to open a criminal investigation into Hillary Clinton’s use of a private email account during her tenure as secretary of state from 2009 through 2013, the New York Times reported late Thursday. The request was reportedly made by two inspectors general, whose names were not revealed.

It is not yet clear whether the Justice Department will accede to the request, the Times reported, citing senior government officials. Clinton, on her part, has repeatedly denied that she shared classified material through her personal email account -- a claim that was reportedly contested by the inspectors general for the State Department in a June 29 memo.

According to the memo, written by the State Department's Under Secretary of State for Management Patrick F. Kennedy and obtained by the Times, Clinton’s private email account contained “hundreds of potentially classified emails.”

The interest in the contents of Clinton’s emails stems from the fact that her use of a private account violated White House and State Department guidelines at the time. The State Department had earlier proposed releasing her emails in January 2016, but the proposal was later rejected by a federal judge who called for them to be made public on a “rolling” basis.

The State Department is currently reviewing around 55,000 pages of the emails. The first batch, containing over 1,900 emails, was released on June 30. In those 3,000 pages, portions of several emails were redacted because they were later upgraded to “classified status.”

However, it is not clear if the information in these emails was marked as classified by the State Department when Clinton sent or received them, the Times reported.

“I did not email any classified material to anyone on my email,” Clinton, who is currently the frontrunner for the Democratic presidential nomination, said in March. “I’m certainly well aware of the classification requirements and did not send classified material.”

The release of her emails, several of which date back to 2009 and deal with the security situation in Afghanistan, Iran and Libya, has been a sticking point in the early stages of Clinton’s presidential campaign.