(CNN) -- A week before Congress is expected to finally hear from CIA contractors on the ground in Libya during the deadly Benghazi attacks, a Republican member said it is long overdue the American public learn the truth of "the murky events of September 11, 2012," that left a U.S. ambassador and three other Americans dead.
"We know what the senior people have said but we don't know what the people who were on the ground are going to say and we need to get those answers," Rep. Devin Nunes (R-California) told CNN by phone Wednesday.
In a letter to House Speaker John Boehner sent Wednesday, Nunes said if questions remain unanswered or "if some answers differ substantially from the established narrative and timeline of the attack, then it would be warranted to take new measures to complete the investigation and synthesize the information obtained by the Intelligence Committees and other committees investigating the Benghazi attack."
Nunes suggested if that occurs, Congress should consider appointing an independent investigator.
Separately, another Republican, Rep. Frank Wolf of Virginia, has called for a special select committee to investigate Benghazi. While most of the House leadership has ignored Wolf's call, 178 fellow Republicans have signed his petition for the special committee. Not one Democrat has signed.
Nunes sits on the powerful House Intelligence Committee which, as CNN first reported, next week is expecting the behind closed-door testimony of three CIA contractors who worked for the intelligence agency when Ambassador Christopher Stevens and the three others were killed.
To date, the only CIA operative on the ground during the attack to testify before the committee has been the No. 2 CIA manager in Libya.
The lack of direct testimony from those on the ground has frustrated a number of congress members who have told CNN they are tired of the Benghazi affair being filtered through the memos prepared by staff and testimony of others who were not in Libya, or were there but have not had the opportunity to give firsthand accounts to elected members.
Nunes outlined the questions he hopes the committee will finally get answers to from witnesses.
Those questions range from why a special State Department-led counterterrorism team was not dispatched as the assault was ongoing to whether the terrorists responsible have been identified but administration officials have failed to authorize a capture/kill operation.
'"We need to identify who -- at the level of presidential cabinet secretaries or at the National Security Council (NCS) -- signed off on the decision NOT to dispatch a FEST team to Benghazi and determine the basis of that decision,'' Nunes wrote.
FEST stands for Foreign Emergency Support Teams, interagency response teams sent to provide assistance to ambassadors. While Nunes writes that it is unlikely the ambassador could have been saved, "the team could have advised, assisted, and coordinated security at the compound and the annex after the attack."
He also wrote it could have aided in the hunt for the perpetrators, noting that the FBI did not reach the area until three weeks after the assault.
Letter raises a series of questions
The Nunes letter also asserts there still is information lacking or discrepancies on other fronts, including:
-- Communications during the attack between the Benghazi annex, the State Department compound where the ambassador and his aide and computer security expert Sean Smith were killed and with other U.S. based agencies; Nunes specifically wants to know whether there was chatter on a classified channel to which no committee would have access.
-- Which terrorist groups had the sophistication to secure the coordinates for the deadly mortar hits on the CIA annex, one of which killed former Navy SEALs Glenn Doherty and Tyrone Woods.
-- The need for a full accounting of purchases made in Benghazi "by the State Department and other government agencies in the year prior to the attack." While Nunes would not elaborate, it has been widely debated on whether the U.S. was involved in a gun-buying mission to be sent to Syrian rebels. A senior intelligence official last week told CNN there was no such operation.
-- Similarly, Nunes said they need a full accounting of all foreigners who met with officials from the State Department and other agencies in the year prior to the attack.
-- Finally, Nunes raises the issue of "possible witness intimidation," saying the committee should investigate whether members of State Department or any government officials in the United States or on the ground in Benghazi were "asked to sign non-disclosure agreements after the attack or asked to undergo polygraph tests? If so, why were those requests made?" he wrote.
CNN has reported some involved in the Benghazi operation have been regularly polygraphed by their employer, the CIA. The agency and its director, John Brennan, have vehemently denied those on the ground were subjected to retaliatory polygraphs and have said the director has encouraged operatives who wish to speak to Congress to come forward.
The CIA says the CNN report is "patently false."
In its statement to the network, the agency said "not a single CIA officer who was on the ground in Benghazi during the attacks has been subjected to any CIA polygraph intended to discourage them from speaking to Congress or as a retaliation."
A spokesman added, "To date, some of these officers have already spoken to the oversight committees on Benghazi."
Benghazi has remained a continuing thorn for the Obama administration as the Republican-led House has had five different committees investigating the conflicting stories of what triggered the terrorist attack and what some critics charge is an absence of a coherent explanation of what Stevens was doing the night he was killed; the military's failure to launch a rescue mission and the CIA's role in Benghazi for months prior to the attack.
The administration initially and stubbornly for several days insisted the Benghazi attack and the first murder of an American ambassador in more than 30 years was the result of a spontaneous demonstration over an anti-Muslim film.
That was later proven wrong in testimony before the various committees.