Dozens of tombs filled with up to 40 mummies each have been discovered around a 1,200-year-old ceremonial site in Peru’s Cotahuasi Valley, according to an April 9 Discovery News report.

According to archaeologists, the tombs are located on small hills surrounding the site, and have excavated seven tombs containing at least 171 mummies from the site, now called Tenahaha. Apparently, before rigor mortis set in, the mummies had their knees put up to the level of their shoulders and their arms folded along their chest, the researchers found. The corpses were then bound with rope and wrapped in layers of textiles.

Archaeologist Justin Jennings, a curator at Toronto’s Royal Ontario Museum, wrote in a chapter of the newly published book “Tenahaha and the Wari State: A View of the Middle Horizon from the Cotahuasi Valley” (University of Alabama Press, 2015), that “The dead, likely numbering in the low thousands, towered over the living.”

Jennings added that the mummies range in age from neonate fetuses to older adults, with some of the youngest mummies (such as infants) being buried in jars. While alive the people appear to have lived in villages close to Tenahaha. The mummified remains were in poor shape due to damage from water and rodents.

Additionally, the researchers found some of the mummies were intentionally broken apart, their bones scattered and moved between the tombs. In one tomb the scientists found almost 400 isolated human remains, including teeth, hands and feet.

Understanding the selective destruction of the mummies and artifacts is a challenge. “In the Andes, death is a process, it’s not as if you bury someone and you’re done,” Jennings told Live Science in an interview.