House Republicans investigating the Benghazi terror attack have acquired a batch of previously undisclosed email correspondence between former Secretary of State Hillary Clinton and her longtime confidant Sidney Blumenthal, indicating that either Clinton or the State Department withheld requested email correspondence, according to Politico.

Through frequent emails sent to Clinton's private email account, Blumenthal provided various advice and intelligence to his former boss, covering topics from Benghazi to political strategy. Much of that advice was then circulated through the State Department by Clinton, according to The Associated Press.

Blumenthal recently had his Benghazi-related emails subpoenaed by the House Select Committee on Benghazi, and shortly before appearing to testify to the committee behind closed doors on Tuesdya, he handed over 60 new emails regarding Libya and the deadly attack on the Benghazi diplomatic compound.

"These emails were not previously produced to the Committee or released to the public, and they will help inform tomorrow's deposition," panel Chairman Trey Gowdy, R-S.C., said in a statement released late Monday evening. "We are prepared to release these emails."

Gowdy said he would like to have the emails released as early as Tuesday, but must first get the ranking Democrat on the committee to agree.

"We are prepared to release these emails, but where practicable our internal processes include consultation with the Ranking Member before release. If Ranking Member Cummings consents, we will add to the former Secretary's public email record and release these shortly. If not, we will do so after the required five days has passed," Gowdy wrote.

The discovery of new emails raise questions as to why the committee wasn't provided the correspondence to begin with.

Because Clinton exclusively used a private email server to conduct official federal business during her tenure at the State Department, rather than the government-provided email, she was ultimately allowed to decide which emails were considered "official" business, and needed to be turned over to the State Department, and which emails were considered private. Those emails deemed private in nature were deleted from her home-based server without third-party oversight.

The 2016 Democratic presidential contender said she turned over all work-related correspondence to the State Department, which was tasked with going through the emails to identify relevant messages to be given to the Benghazi panel. Earlier this year, officials ended up turning over about 300 emails related to Benghazi, but at least 60 related emails were withheld, until now.

Politico's "congressional source did not know whether Clinton had turned over all the new emails to State and State did not provide them, or whether Clinton failed to hand over the correspondence."

When State Department spokesman Alec Gerlach was asked why the Blumenthal emails were not originally produced, he said the department would need to see the emails before responding.

"The department is working diligently to publish to its public website all of the emails received from former Secretary Clinton through the FOIA process," Gerlach said in a statement. "We provided the committee with a subset of documents that matched its request and will continue to work with them going forward. Secretary Kerry has been clear that the State Department will be both transparent and thorough in its obligations to the public on this matter."