ABC News’ Martha Raddatz and Luis Martinez report:

U.S. Central Command has launched an investigation into the circumstances behind this weekend’s deadly NATO airstrikes along Afghanistan’s rugged border with Pakistan that resulted in the deaths of more than two dozen Pakistani soldiers.

Centcom Commander Gen. James Mattis has appointed Brig. General Stephen Clark, from Air Force Special Operations Command, to head up the investigation into the airstrikes and directed him to provide an initial report by Dec. 23.

Mattis has directed Clark to include representatives from NATO,  Pakistan and Afghanistan as part of his investigation.   A  Centcom press release announcing the investigation says it is the command’s intent “to include these government representatives to the maximum extent possible to determine what happened and preclude it from happening again.”

The release says the investigative team “will focus their efforts on the facts of the incident and any matters that facilitate a better understanding of the circumstances surrounding the deaths and injuries of the Pakistan forces.”

“Fog of war” is  how a senior military official described this weekend’s  deadly incident along the Afghanistan Pakistan border to ABC News.

The official says there are still conflicting reports about what happened, though he characterized how hard it must be for the Pakistanis to lose so many of their men to “friendly fire.”   He described the Pakistani reaction as being what  it must have been like “for us to lose all those Navy SEALS, but worse because it was friendly fire. ”

The official said there are still details that have to be fleshed out about the incident, but said there was ” a lot of shooting going on” when the close air support was called in.  He also noted there are conflicting reports about whether it was helicopters or fixed wing aircraft that killed the Pakistanis.

The official  described a situation where U.S. forces thought they were looking at “someone” and it turned out to be “someone else.”