The officials say they obtained the information about the Nusra Front's leader, Abu Mohammad al-Golani, after capturing members of another al-Qaida group.
They said the men gave them the first known photograph of al-Golani and letters written by the militant leader.
The officials spoke today on condition of anonymity because they weren't authorized to speak to journalists.
They gave The Associated Press al-Golani's photo and letter excerpts. It wasn't immediately clear when the letters were written.
One UN worker was kidnapped for eight months in Syria and was released in October. Another two dozen UN peacekeepers were briefly held this year.