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 ChaffetzJason ChaffetzChaffetz probing national park's tweet welcoming a national monument A guide to the committees: House GOP rep pushes back on Trump's tweet about town hall protests MORE (R-Utah) and Sen. Lindsey GrahamLindsey GrahamDem senator asks for 'top to bottom' review of Syria policy A guide to the committees: Senate Cheney to intro Pence at Jewish GOP event 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 McCainJohn McCainA guide to the committees: Senate Webb: The future of conservatism New national security adviser pick marks big change on Russia MORE (Ariz.), Kelly AyotteKelly AyotteLewandowski saw no evidence of voter fraud in New Hampshire NH governor 'not aware’ of major voter fraud Former NH AG: 'Allegations of voter fraud in NH are baseless' MORE (N.H.), Ron JohnsonRon JohnsonA guide to the committees: Senate Hopes rise for law to expand access to experimental drugs Dems ask for hearings on Russian attempts to attack election infrastructure MORE (Wis.) and Reps. Darrell Issa (Calif.), Trey GowdyTrey GowdyA guide to the committees: House Congress asserts itself GOP rep says media is 'blurring' fact and opinion 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.