“We have had some challenges securing the site,” Nuland said. “We are continuing to talk to the Libyan side about that.”

It was unclear how long the FBI agents would remain in Benghazi after their arrival Thursday – 23 days after the attack – or how freely they will be allowed to pursue the investigation.

In the days after the attack, Benghazi residents rose up in anger against suspected Islamist militants suspected in the attack, but the city’s respite from their influence was short-lived.

A week ago, a police station near Benghazi’s Al Jalaa hospital was attacked by a mob of supporters of the principle group blamed in the consulate attack, Ansar al Shariah. The attackers threw grenades at the police station and sprayed gunfire at four police vehicles. Two of the gunmen were allegedly wearing suicide bomb vests.

On Tuesday, six police officers were injured during several attacks, although the exact details remain sketchy. Two other policemen from the Gar Younis police station were injured when a bomb was thrown at the station.

Another four police officers were reported to have been wounded in two separate attacks near a children’s hospital the same day. In a separate incident, two military personnel were wounded in an explosion from a rocket-propelled grenade shortly after midnight Tuesday, one seriously. A grenade attack against a police checkpoint took place several hours later.

Pentagon spokesman George Little said that the U.S. military had provided protection and transport for the FBI agents, but he offered few other details of the agents’ arrival in Benghazi. When asked how reporters were able to visit the compound on many occasions since the attack while it took the U.S. military three weeks to arrive, he said the military went to Benghazi at the request of the State Department.

“The U.S. military has been willing to consider requests at various points,” Little said. “This is really a question best directed to the State Department and FBI.”

Little described the deployment as a support mission only. He declined to say how many U.S. troops were providing security and would not say how many FBI agents had been sent to Benghazi.

Little also noted that everyone involved had been anxious to get the investigation moving. He called the investigation aggressive.

“We’ve not been sitting around waiting for information to come to us,” he said.

McClatchy special correspondent Mel Frykberg contributed to this story from Cairo.