(CNN) -- More than two weeks after four Americans -- including the U.S. ambassador to Libya -- were killed in an attack on the U.S. Consulate in Benghazi, FBI agents have not yet been granted access to investigate in the eastern Libyan city, and the crime scene has not been secured, sources said.
"They've gotten as far as Tripoli now, but they've never gotten to Benghazi," CNN National Security Analyst Fran Townsend said Wednesday, citing senior law enforcement officials.
Last Thursday, U.S. Secretary of State Hillary Clinton told reporters that an FBI team had reached Libya earlier in the week.
"In fairness to the secretary, it may be that she wanted to be coy about where they were in Libya for security concerns. That's understandable. But the fact is, it's not clear they've been in Libya for very long," Townsend said on CNN's "Anderson Cooper 360°."
"They had difficulty, and we understand there was some bureaucratic infighting between the FBI and Justice Department on the one hand, and the State Department on the other, and so it took them longer than they would have liked to get into country. They've now gotten there. But they still are unable to get permission to go to Benghazi."
FBI agents have made a request through the U.S. State Department for the crime scene to be secured, Townsend said, but that has not happened.
"The senior law enforcement official I spoke to said, 'If we get there now, it's not clear that it will be of any use to us,'" Townsend said.
The FBI team has conducted interviews of State Department and U.S. government personnel who were in Libya at the time of the attack, Townsend said, but the FBI's request to directly question individuals who Libyan authorities have in custody was denied.
Libyan officials have said they have brought in dozens of people for questioning since the September 11 attack, which officials said occurred amid a large protest about a U.S.-made film that mocked the Muslim Prophet Mohammed.
U.S. Ambassador Chris Stevens was one of four Americans slain in the assault, which has fueled increased global scrutiny of the North African nation and increased political sparring in the United States over the investigation into who was behind it.
Speaking to reporters last Thursday, White House spokesman Jay Carney said the assault was a "terrorist attack."
At the United Nations Wednesday, Clinton referenced the attack in remarks about violent extremism.
"Now, with a larger safe haven and increased freedom to maneuver, terrorists are seeking to extend their reach and their networks in multiple directions," she said. "And they are working with other violent extremists to undermine the democratic transitions underway in North Africa, as we tragically saw in Benghazi."
On Wednesday, Townsend said a law enforcement source told her investigators from day one "have known clearly that this was a terrorist attack."
But officials have offered conflicting assessments of the attack, with initial accounts alleging that protesters angry about the film fueled the violence.
That approach has drawn sharp criticism from Republican lawmakers.
On Sunday, the chairman of the House Intelligence Committee told CNN there was no proof indicating the attack was related to protests over an anti-Islam video.
Republican lawmakers echoed that argument on "AC 360" Wednesday.
"I do not understand the continuance of the president to look the other way and not admit the fact that this was obviously a terrorist attack," said U.S. Sen. Johnny Isakson, R-Georgia. "And I cannot believe that the FBI is not on the ground yet, and there's not enough cooperation to get there."