* U.S. ambassador and 3 others killed in original attack
* Security source says U.S. agents now collecting evidence
* FBI has no immediate comment
BENGHAZI, Libya, Oct 4 (Reuters) - A team of U.S. investigators travelled to the eastern Libyan city of Benghazi on Thursday to visit the compound where the U.S. ambassador was killed in an attack last month, Libyan security sources said.
FBI agents were dispatched to Libya after the Sept. 11 assault on the U.S. diplomatic mission and on another facility in which Ambassador Christopher Stevens and three other Americans were killed.
But, until now, the agents have remained in Tripoli.
"An American team has been visiting the compound," one Libyan security source said. Another security source said: "They have been assessing the damage, collecting evidence."
They did not give further details and the FBI in Washington had no immediate comment.
The road leading to the compound's front gate was blocked off by vehicles mounted with weapons belonging to the Libyan security forces, a Reuters witness said.
Libyan Deputy Foreign Minister Mohammed Abdel Aziz said on Tuesday that the FBI team would soon be heading to Benghazi but said that Tripoli and Washington had yet to agree on how the two sides would conduct a joint investigation.
U.S. Secretary of State Hillary Clinton on Wednesday vowed every effort would be made to try to piece together a full account of the attack on the U.S. consulate "wherever that leads," but cautioned that it could take time for a complete picture to emerge.
Libyan officials say eight people have so far been arrested in connection with the attack.