Details emerge about Americans badly injured in Benghazi attack

In addition to the four Americans killed in the Benghazi terror attack last year, at least two other Americans were severely injured in the fighting that night, Fox News has learned.

The injuries were sustained by U.S. personnel after mortars struck the CIA annex rooftop they were defending. Fox News is told that one former government contractor -- who is expected to testify this week along with four other contractors in classified sessions on Capitol Hill -- has had multiple surgeries since the attack and has still not regained full use of one arm.

The blood loss after the attack was so severe that a source close to the contractor said it had been life-threatening.

In addition to former Navy Seals Tyrone Woods and Glen Doherty, who were killed defending the Annex, at least two other Americans were severely injured on the roof top.

Diplomatic Security Agent David Ubben – who as late as August was still recovering at Walter Reed Medical Center in suburban Washington - was so severely injured fighting alongside the Seals that he has undergone multiple surgeries.  The protocol is often referred to as a “leg or limb salvage.”

Little is known about those who survived the Benghazi attack. The State Department confirmed in March, after multiple inquiries by Fox News, that a total of three diplomatic security agents, as well as a State Department contractor, were among the Americans injured during the terrorist assault which killed the two former SEALs, Ambassador Chris Stevens, and Foreign Service Officer Sean Smith.

The latest details are emerging as the House Intelligence Committee hears this week from contractors who were on the ground in Benghazi. Fox News has learned that they will give their accounts in closed, classified sessions on Wednesday and Thursday.

Two contractors were expected to appear Wednesday, and three former government contractors from the CIA annex are expected Thursday, according to sources familiar with the meetings.

In a press release from earlier this year, the intelligence committee appeared to identify this week's witnesses, adding that they included those who signed a book deal earlier this year. "The Subcommittee will pursue interviews with three additional CIA personnel who are publishing a book and whose public comments suggest possible contradictions with testimony the Intelligence Committee has received on the record," the release said.

The lawyer who represents the authors would not comment on their Capitol Hill appearance, adding that they were part of "an elite security team" in Benghazi.

While the sessions are not open to the public, sources told Fox News that the timeline offered by some of the contractors may differ from the public narrative that there were two distinct waves to the attack -- first at the consulate at approximately 9:40 p.m. local time and then at the CIA annex the following morning, separated by a lull in the fighting.

The fighting was characterized to Fox News as being more "constant, consistent" throughout the attack's seven-hour duration.  If there was no lull in the fighting, it raises more questions about the lack of a significant military response to the Benghazi assault -- during that time, Stevens' whereabouts were unknown.

In a letter to House Speaker John Boehner last week, Rep. Devin Nunes, R-Calif., stated that any discrepancies demanded further investigation. "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."