The troops are deployed there in support of President Donald Trump's executive order to secure the U.S.-Mexico border.
A defense official speaking on the condition of anonymity to provide additional details not yet made public said the accident occurred in a civilian vehicle, but no civilians were harmed in the incident.
The incident did not involve any of the scores of Stryker vehicles the Pentagon has sent down to the border to perform patrols, the official said.
The accident occurred around 8:50 a.m. MDT Tuesday; the names of the deceased will not be released until the next of kin are notified.