Republican lawmakers are pressing James Comey, the new FBI director, to step up the bureau’s investigation of the deadly 2012 attack on the U.S. mission in Benghazi, Libya, calling the administration’s efforts “simply unacceptable.”

Rep. Jason Chaffetz Jason ChaffetzTop Utah paper knocks Chaffetz as he mulls run for governor: ‘His political career should be over’ Boehner working on memoir: report Former GOP lawmaker on death of 7-year-old migrant girl: Message should be ‘don't make this journey, it will kill you' MORE (R-Utah) and Sen. Lindsey Graham Lindsey Olin GrahamWhite House pleads with Senate GOP on emergency declaration GOP lawmaker says panel to investigate drug company gaming of patent system Sixteen years later, let's finally heed the call of the 9/11 Commission MORE (R-S.C.) are spearheading the effort with a draft letter to Comey, demanding the FBI director brief Congress on his work in the next month.

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"It has been more than 10 months since the attacks," the draft letter, first reported by CNN, reads. "We appear to be no closer to knowing who was responsible today than we were in the early weeks following the attack. This is simply unacceptable.

"We encourage you to be aggressive in your investigation to properly hold accountable those who attacked our compounds in Benghazi," the letter adds. "We owe the families of those killed, and the people of this nation, answers to who was responsible and ensure they are held accountable."

The deadly attack claimed the lives of four Americans, including Ambassador Christopher Stevens.

Chaffetz confirmed the letter on Fox News on Wednesday, claiming some of the suspects in the investigations continue to live in Benghazi but the FBI has never talked to them.

Other lawmakers signing the letter include Sens. John McCain John Sidney McCainGOP lobbyists worry Trump lags in K Street fundraising Mark Kelly kicks off Senate bid: ‘A mission to lift up hardworking Arizonans’ Gabbard hits back at Meghan McCain after fight over Assad MORE (Ariz.), Kelly Ayotte Kelly Ann AyotteBottom Line US, allies must stand in united opposition to Iran’s bad behavior American military superiority will fade without bold national action MORE (N.H.), Ron Johnson Ronald (Ron) Harold JohnsonWhite House pleads with Senate GOP on emergency declaration White House, GOP defend Trump emergency declaration GOP senator says Republicans didn't control Senate when they held majority MORE (Wis.) and Reps. Darrell Issa (Calif.), Trey Gowdy Harold (Trey) Watson GowdyThe family secret Bruce Ohr told Rod Rosenstein about Russia case Trey Gowdy joins Fox News as a contributor Congress must take the next steps on federal criminal justice reforms MORE (S.C.) and Jim Jordan (Ohio).

The lawmakers hope to deliver the letter to Comey on Wednesday or Thursday, according to CNN.

The letter comes two days after the Senate confirmed James Comey to lead the FBI on a 93-1 vote.

The FBI faced criticism immediately after the attack when news reports indicated that it did not reach scene to investigate until weeks after the assault.

Republican lawmakers have questioned if the administration could have done more to prevent the attack and responded quickly.

The Obama administration also faced intense criticism for initial talking points that claimed the attack was the result of protests over an anti-Islam video, later acknowledging that it was a planned terrorist operation.