The first bones from the grave were unearthed late last year
Archaeologists have found a mass grave in Mexico City with at least 49 human skeletons dating from Spain's conquest of the Aztecs in the 16th Century.
Experts say the site is unusual as the Aztec skeletons are carefully laid out and bear marks of European traditions.
The find was made in the Tlatelolco area of Mexico City, where the Indians made a last stand against the Spanish.
Many died in the fighting and afterwards many others succumbed to disease and epidemics.
"We were completely taken by surprise. We didn't expect to find this massive funeral complex," said Salvador Guilliem of the city's archaeology institute.
Mr Guilliem said he thought the people buried at the site died in the battle against the invading Spanish or fell victim to the disease that wiped out large swathes of the native population after Spain won control of the city in 1521.
The new find differs from other burial sites in the Tlatelolco area where the bodies have been dumped unceremoniously into pits.
Those found by Mr Guilliem follow Christian customs, with the bodies laid on their backs with arms crossed over the chest. They were not placed in coffins, but wrapped in large maguey cactus leaves.
Exacavations are continuing at the site
Artefacts lying with the bodies are from a pre-Hispanic era, Mr Guilliem said, indicating that the burials, discovered in late 2008, were ordered by Spanish overlords but carried out by Aztecs.
The dead, almost exclusively adults, also had many characteristics of warriors. All but four were young men, most were tall and several showed broken bones that had healed.
Skeletons of two children, a teenager, and an older person wearing a ring possibly signifying an elite status, were also found in the tomb.
The archaeologists say they expect to find at least 50 more skeletons as excavations at the huge Tlatelolco complex continue. There are some 67 ancient structures in the area, including several massive pyramids.