The remains of what appear to be four US soldiers who died in 1846 during the Mexican-American war have been found, Mexican officials have said.
The skeletons were found at the site of the Battle of Monterrey in northern Mexico alongside relics indicating the bodies were US soldiers.
Mexico lost the battle and the war, ceding much territory to the US.
Experts had previously thought the site contained a mass grave for Mexicans but only the US troops have been found.
Measurements of the skulls and bones, plus US coins and other items found with the skeletons, have led Mexican archaeologists to conclude the remains are US war dead.
Mexico's state archaeological agency said the bodies were found in several digs between 1996 and 2008 but it took a long time to identify the remains because it was believed only Mexicans were buried at the battle site.
An official with the agency told the Associated Press news agency there were plans to carry out DNA tests and inform the soldiers' relatives, if possible.
"There are proposals... to return those individuals found so far to the United States, and for them to return those that they have from battles that took place in their country," said the National Institute of Anthropology and History in a statement quoted by AP.