As they wrap up their 13-month probe into the terrorist attacks in Benghazi that killed four Americans, congressional investigators have zeroed in on a press release issued the day before the murders by White House Press Secretary Jay Carney.

They also are seeking fresh testimony from former Defense Secretary Leon Panetta.

Staffers with the House Armed Services Subcommittee on Oversight and Investigations told Fox News they have reached the preliminary conclusion – as the Obama administration has long maintained – that no military rescue or remedy was feasible on the night of September 11, 2012, when U.S. Ambassador to Libya Chris Stevens and three other Americans died amid an eight-hour assault by terrorists on the U.S. consulate in Benghazi and a nearby annex.

However, House investigators have also determined that the reason no military forces could be rallied to intervene in Benghazi is because U.S. military assets were poorly postured amid the turmoil of that period, as the eleventh anniversary of the September 11, 2001 attacks approached.

“My job was to look at the days and the weeks and the months and the years leading up to that day, and ask the question: Why weren’t we prepared, and who is responsible?” said Rep. Martha Roby, R-Ala., chair of the HASC subcommittee. “If the White House is projecting that we were safe, the White House has to take responsibility of our lack of preparedness.”

On September 10, 2012, the day before the Benghazi attacks, Carney’s office issued a four-sentence press release stating that earlier that day, President Obama had met with “key national security principals” to discuss “the steps taken to protect U.S. persons and facilities abroad…on the eve of the eleventh anniversary of September 11th.”

General Carter Ham, then the commander of U.S. Africa Command, the combatant command with jurisdiction over Libya, told the House investigators he was not consulted as part of the meetings referred to in the White House press release.

When a spokesperson for the National Security Council indicated that the White House had dealt directly with the chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey, the House Armed Services subcommittee called the chairman as a witness in a classified setting. Committee staffers told Fox News that Dempsey indicated to them last week that the meetings alluded to in the press release had been routine, and fairly casual in nature.

Questioned about the scope of the security meetings held in the period leading up to the Benghazi attacks, and the development of the September 10 press release, Carney bristled at what he deemed “partisan” inquiries by the GOP-controlled majority on the House Armed Services Committee. He also suggested that questions about those meetings were not properly addressed to the spokesman for the commander-in-chief.

“I think when it comes to how the U.S. military positions its assets,” Carney said in response to queries posed at the daily press briefing on Thursday, “that is a question best answered by the Department of Defense and by commanders. But you get no argument here from the suggestion that there was not adequate security there.”

Because its jurisdiction is limited to the U.S. military, the subcommittee cannot subpoena White House documents or witnesses. But staffers on the panel told Fox News they are working in tandem with other House committees whose purview may enable them to secure such evidence.

Asked if the White House would be willing to share with the panel, or make available to the public any emails, memos or other documents associated with the development of the press release, Carney shook his head and said, “I think we’re done here,” before exiting the briefing room.

Roby indicated the panel will seek to question former Defense Secretary Panetta as part of its probe, to see what he can share regarding the security precautions alluded to in the White House document.

During a “Fix the Debt” panel at the National Press Club on Wednesday, in which Panetta participated, Fox News attempted to pose a question about this to the former secretary. But the moderator forbade it and Panetta’s office did not respond to an attempt by Fox News to discuss the subject off-camera.

Staffers for the subcommittee said they hope to produce a final report summarizing their findings before work begins in earnest on the next defense authorization bill. They also said the Pentagon has generally been “very cooperative” with the panel in making documents and witnesses available, and has not sought to “stonewall” their investigation.