CALPULALPAN, Mexico (Reuters) -- Skeletons found at an unearthed site in Mexico show Aztecs captured, ritually sacrificed and partially ate several hundred people traveling with invading Spanish forces in 1520.

Skulls and bones from the Tecuaque archeological site near Mexico City show about 550 victims had their hearts ripped out by Aztec priests in ritual offerings, and were dismembered or had their bones boiled or scraped clean, experts say.

The findings support accounts of Aztecs capturing and killing a caravan of Spanish conquistadors and local men, women and children traveling with them in revenge for the murder of Cacamatzin, king of the Aztec empire's No. 2 city of Texcoco.

Experts say the discovery proves some Aztecs did resist the conquistadors led by explorer Hernan Cortes, even though history books say most welcomed the white-skinned horsemen in the belief they were returning Aztec gods.

"This is the first place that has so much evidence there was resistance to the conquest," said archeologist Enrique Martinez, director of the dig at Calpulalpan in Tlaxcala state, near Texcoco.

"It shows it wasn't all submission. There was a fight."

The caravan was apparently captured because it was made up mostly of the mulatto, mestizo, Maya Indian and Caribbean men and women given to the Spanish as carriers and cooks when they landed in Mexico in 1519, and so was moving slowly.

The prisoners were kept in cages for months while Aztec priests from what is now Mexico City selected a few each day at dawn, held them down on a sacrificial slab, cut out their hearts and offered them up to various Aztec gods.

Some may have been given hallucinogenic mushrooms or pulque -- an alcoholic milky drink made from fermented cactus juice -- to numb them to what was about to happen.

Teeth marks

"It was a continuous sacrifice over six months. While the prisoners were listening to their companions being sacrificed, the next ones were being selected," Martinez said, standing in his lab amid boxes of bones, some of young children.

"You can only imagine what it was like for the last ones, who were left six months before being chosen, their anguish."

The priests and town elders, who performed the rituals on the steps of temples cut off by a perimeter wall, sometimes ate their victims' raw and bloody hearts or cooked flesh from their arms and legs once it dropped off the boiling bones.

Knife cuts and even teeth marks on the bones show which ones had meat stripped off to be eaten, Martinez said.

Some pregnant women in the group had their unborn babies stabbed inside their bellies as part of the ritual.

In Aztec times the site was called Zultepec, a town of white-stucco temples and homes where some 5,000 people grew maize and beans and produced pulque to sell to traders.

Priests had to be brought in for the ritual killings because human sacrifices had never before taken place there, Martinez said.

On hearing of the months-long massacre, Cortes renamed the town Tecuaque -- meaning "where people were eaten" in the indigenous Nahuatl language -- and sent an army to wipe out its people.

When they heard the Spanish were coming, the Zultepec Aztecs threw their victims' possessions down wells, unwittingly preserving buttons and jewelry for the archeologists.

The team, which began work here in 1990, also found remains of domestic animals brought from Spain, like goats and pigs.

"They hid all the evidence," said Martinez. "Thanks to that act, we have been allowed to discover a chapter we were unaware of in the conquest of Mexico."