WASHINGTON — A House Intelligence Committee investigation of the Sept. 11, 2012, attacks on U.S. outposts in Benghazi concludes that while the Central intelligence Agency had properly secured its compound in the Libyan city, the State Department knew its security precautions were inadequate at the U.S. Special Mission where U.S. Ambassador Chris Stevens died.

But the report, while offering rich and previously unknown details about the hours-long attack on the two facilities, still leaves unanswered a key question: If, as the report states, the CIA station chief in Tripoli, State Department diplomatic security agents and CIA contractors in Benghazi knew the mission wasn’t properly secured, why was Stevens allowed to stay there for what was supposed to be a four-day visit?

Indeed, security appeared lax even after 80 attackers had stormed the sprawling four-building complex when CIA contractors arrived to offer assistance, the report said. “The CIA security team observed that some, perhaps all, of the (diplomatic security) agents were unarmed and one of them was not wearing shoes,” the report said.

The bipartisan report, the result of a two-year-long investigation by the House Permanent Select Committee on Intelligence, was released without fanfare Friday night, the latest in a series of probes that have sought to explain what happened at Benghazi, whether the attacks could have been prevented and why the Obama administration gave an incorrect accounting of what took place. In addition to Stevens, three other Americans died in what became a hot political issue in the run-up to the 2012 election and is likely to figure in the 2016 presidential campaign, especially if then-Secretary of State Hillary Clinton is the Democratic candidate.

The report concluded that neither the CIA nor the U.S. military delayed their response to the attack, refuting Republican accusations that a slow response was in part responsible for Stevens’ death. It also refuted claims that Obama administration officials deliberately misled the public when they said a spontaneous protest had sparked the attack; that information, while incorrect, had come from CIA analysts, the report said.

Still, it concluded that the State Department knew the Special Mission could not fend off a major attack at a time when attacks against Westerners in Benghazi were rising. The intelligence community, the report said, had written 429 “cables, reports and assessments” on security in Libya between February and October 2012.

“CIA security personnel testified that State Department (diplomatic security) agents repeatedly stated they felt ill-equipped and ill-trained to contend with the threat environment in Benghazi,” the report said. “According to eyewitnesses … the DS agents knew well before the attacks that they could not defend the (Special Mission) against an armed assault.”

The report said that State Department security agents had told their CIA counterparts that they had requested “additional resources” and that those requests were “with the U.S. Embassy in Tripoli.”

“The CIA security contractors noted the security flaws of the (Special Mission),” the report said. “In their view, it was a very large compound with too few guards and large spaces for attackers, such as snipers, to hide.”

The report for the first time offered a reason for the attack: revenge for a U.S. drone strike in Pakistan that killed Abu Yahya al-Libi, a top al-Qaida operative. Al-Qaida announced his death hours before the attack began.

It also provided for the first time an explanation for why the CIA had a station in Benghazi, refuting persistent rumors that the CIA was using Benghazi to funnel weapons to Syrian rebels. Instead, the report said, the CIA was using its Benghazi station to track weapons smuggling from Libya to Syria — the first official indication that within months of the demise of Libyan leader Moammar Gadhafi, U.S. officials were aware that Benghazi had become an important source for weapons reaching Syria.

“The CIA’s mission in Benghazi was to collect foreign intelligence … about foreign entities that were themselves collecting weapons in Libya and facilitating passage in Syria,” the report said.

The report concludes the CIA repeatedly and “specifically highlighted the threats to Western interests in Libya” in the run-up to the attack but had no intelligence that the U.S. Special Mission or the annex would be attacked that night. The only intelligence of that came from a member of the Transitional National Security council who heard about the attack “very shortly” beforehand and informed the Libyan government. That information did not reach the U.S. personnel there.

“There is no evidence of intelligence failure,” the report concluded.

The report also for the first time reveals that an unmanned Predator drone that arrived over the Benghazi mission about 90 minutes after the attack began had been flying over the restive eastern Libyan city of Derna to Benghazi before it was diverted. Derna has long been fertile ground for jihadists and was a likely transit point for weapons traveling to Syria.

And for the first time, the U.S. government publicly said that Abu Sufian bin Qumu, the leader of the Libya-based Ansar al Sharia terrorist group’s Derna section, was “probably” involved somehow in the attack, even as he was a five-hour drive away from Benghazi in Derna.

The report also reveals new details about the chaos that surrounded the response to the attack. It said CIA security contractors at a CIA annex not far from the mission were prepared to leave to render assistance within five minutes of learning of the attack, but that it took them 42 minutes to make the 1.4-mile drive because attackers had blocked the roads. By the time they arrived, the compound’s buildings were ablaze, and Stevens and Sean Smith, a foreign service information management officer, were dead from smoke inhalation.

The nearby CIA annex itself came under attacks that were far more sophisticated, the report said, than what had taken place at the special mission, including three precise mortar barrages that in the space of a minute and nine seconds killed two former Navy SEALs who were part of the CIA security team, Glen Doherty and Tyrone Woods.

The report also described about three hours of chaos at the airport when additional security personnel arrived in Benghazi from Tripoli. A truck they had expected to meet them at the airport did not arrive, the Libyan general who had supposedly arranged for the transport had turned off his cellphone, and Libyan militiamen who were at the airport were unwilling to travel to the hospital where the Americans believed Stevens was being treated. The arriving Americans were uncertain which of the militias they could trust, the report said.

Stevens was making his first visit to Benghazi since becoming ambassador the previous May. According to the report, Stevens had a “long conversation” with the CIA station chief in Tripoli about the security issues a few days before the attack. But the report does not say who decided that it would be safe for Stevens to travel there.

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