Sens. John McCain (R-Ariz.), Lindsey Graham (R-S.C), Kelly Ayotte (R-N.H.) and Saxby Chambliss (R-Ga.) reached out to the heads of the Office of National Intelligence, CIA and other administration officials for more information on the attack, which left four Americans dead including U.S. Ambassador Chris Stevens.
"It is important for the intelligence community to clarify the confusion that still surrounds the administration's initial explanation of the attack in Benghazi," the GOP lawmakers wrote. "This matter raises many critical questions for Congress to consider further."
Specifically, the Senators want information on whether any intelligence on potential threats to the Benghazi facility had been available to the Pentagon or State Department prior to the attack.
The lawmakers also want details on the analysis that led White House officials to initially determine the raid was the result of a anti-U.S. protest gone awry, according to the letter.
That said, the letter also demands information on the intelligence analysis conducted between the release of the official protest scenario and the eventual White House admission the attack was the work of Libyan terrorists.
"Was there no credible evidence at that late date that was compelling enough for the intelligence community and the senior policymakers to draw a conclusion with at least moderate confidence that the attack in Benghazi was a terrorist act?" the letter states.
Tuesday's letter was the latest in a chain of correspondence between McCain, Graham, Ayotte and the White House on what exactly happened that night at the U.S. Consulate in Libya.
The Republican Senators initially sent a letter to U.N. Ambassador Susan Rice, seeking an explanation as to why she claimed the Benghazi attack was a "spontaneous reaction" to a protest, and not a well coordinated attack on American officials by extremists.
In response, Rice told the lawmakers her early assessment on the cause of the Benghazi strike was based on information provided by the intelligence community.
The timing of the letter as Brennan is meeting with top Libyan military and intelligence leaders in Tripoli to discuss the circumstances surrounding the raid.
Senior Libyan interior ministry official Brig. Abdel Moneim al-Tunsi reportedly leaked details Brennan's visit to Tripoli on Monday, according to media reports in the region.
The letter's release also comes a day before a scheduled House Committee on Oversight and Government Reform hearing on the Libya attack.
Called by panel Chairman Rep. Darrell Issa (R-Calif.), the hearing will focus on alleged oversights and gaps in security at the Consulate in the run up to the attack.
Since the Benghazi assault, Marine Corps units attached to the Defense Department's Fleet Anti-Terrorism Security Teams (FAST) were sent to Libya and Tunisia to protect American diplomats and personnel stationed there.
That said, the Pentagon, as well as the State and Justice departments, are launching an overall review of the security situation in Libya prior to the terrorist attack.
Defense Department officials are assembling a team of experts to participate in the inter-agency review, Pentagon press secretary George Little told reporters on Thursday.
"We're forming a team of experts who will look into this over the coming months," Little told reporters at the Pentagon. "It's important that we get to the facts here."