A U.S. law enforcement official confirms to CBS News that the FBI is now assisting the military in its investigation of thethat resulted in the deaths of four U.S. soldiers
The FBI is not taking over the investigation, but the agency's involvement comes as a number of questions have been raised about the ambush.
The Wall Street Journal first reported the FBI involvement. According to the Journal, the FBI is helping to gather and evaluate evidence about the militants who are thought to have attacked the U.S.-Nigerien patrol.
As CBS News' David Martin has reported, the troops were on patrol about 120 miles north of the capital. The risk of enemy contact had been evaluated as very low, so they did not have the kind of air cover that would be ready for a direct-action mission, in which the troops would have been prepared for direct combat. French aircraft were the first to respond, about 30 minutes after the ambush was reported.
Another question Martin pointed out is how it was the signs of a coming ambush were missed. The group of about 50 militants was well-trained, well-equipped and well-organized, Martin noted, and it's surprising that their activity went undetected before the ambush.
The circumstances of Sgt. La David Johnson's death has raised questions, too. After the ambush ended, Johnson was believed by the Pentagon to be alive. For several hours, the military tracked a locator beacon which eventually faded out. His body was not recovered for another two days. Johnson has received more attention because of the, Myeshia Johnson, earlier this week.
The FBI has been involved in the investigations of other recent ambushes of U.S. military overseas including last year's attack on soldiers in Jordan.
CBS News' Andres Triay contributed to this report.