The burial site, known as Las Llamas, contains the skeletons of 140 children who were aged between five and 14 when they were ritually sacrificed during a ceremony about 550 years ago, archaeologists said on Friday.

The site, located near the city of Trujillo, also contained the remains of 200 young llamas apparently sacrificed on the same day.

The burial site was apparently built by the Chimú empire. It is thought the children were sacrificed as floods caused by the El Niño weather pattern ravaged the Peruvian coastline.

“They were possibly offering the gods the most important thing they had as a society, and the most important thing is children because they represent the future,” said Gabriel Prieto, an archaeology professor at Peru’s National University of Trujillo, who has led the excavation along with John Verano of Tulane University.

“Llamas were also very important because these people had no other beasts of burden; they were a fundamental part of the economy.”

Prieto said the children were buried facing the sea, while the llamas faced the Andes mountains to the east.

Excavation work at the burial site started in 2011, but the findings were first published on Thursday by National Geographic, which helped finance the investigation.

Prieto said researchers also found footprints that have survived rain and erosion. The small footprints indicate the children were marched to their deaths from Chan Chan, an ancient city 1.5km (one mile) from Las Llamas, he said.

Verano said the children’s skeletons contained lesions on their breastbones, which were probably made by a ceremonial knife. Dislocated ribcages suggest whoever was performing the sacrifices may have been trying to extract the children’s hearts.

Jeffrey Quilter, the director of the Peabody Museum of Archaeology and Ethnology at Harvard University, described it as a “remarkable discovery”.

Quilter said the site provides “concrete evidence” that large-scale sacrifices of children occurred in ancient Peru.

“Reports of very large sacrifices are known from other parts of the world, but it is difficult to know if the numbers are exaggerated or not,” Quilter said.

Quilter is heading a team of scientists who will analyse DNA samples from the children’s remains to see if they were related and figure out which areas of the Chimú empire the sacrificed youth came from.

Several ancient cultures in the Americas – including the Maya, the Aztec and the Inca, who conquered the Chimú in the late 15th century – practised human sacrifices, but the mass sacrifice of children is something that has rarely been documented.

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