Archaeologists in northern Peru say they have found evidence of what could be one of the world’s largest single cases of child sacrifice.

The pre-Columbian burial site, known as Las Llamas, contains the skeletons of 140 children who were between the ages of 5 and 14 when they were ritually sacrificed during a ceremony about 550 years ago, experts who led the excavation told The Associated Press on Friday.

The site, located near the modern day 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 ancient Chimu empire. It is thought the children were sacrificed as floods caused by the El Niño weather pattern ravaged the Peruvian coastline.