Washington (CNN) The Department of Defense has said it expects the investigation into the October 4 ambush in Niger that killed four US soldiers to be completed by January, according to a statement released Wednesday.

The Pentagon has updated the families of the soldiers killed on the timeline of the investigation.

"Families were informed that AfriCom's investigation team will travel to locations in the US, Africa and Europe to gather information related to the investigation," the statement said. "US Army Maj. Gen. Roger Cloutier, AfriCom's chief of staff, will lead the command's investigation team."

The statement added that the families had been told that the "investigation is expected to be completed in January 2018, but that if circumstances require additional time, that they will be kept informed."

"The Department of Defense is committed to a thorough and detailed investigation into the deaths of Staff Sgt. Bryan C. Black, Staff Sgt. Jeremiah W. Johnson, Staff Sgt. Dustin M. Wright, and Sgt. La David T. Johnson. Once the investigation is completed, briefing the families of the fallen will be the Department's first priority," the statement also said.

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