If you’ve ever wondered how buildings become haunted, here’s a data point: construction workers digging the foundation for a new apartment complex in Philadelphia recently uncovered dozens of centuries-old coffins buried on the site.

CBS Philadelphia is reporting that the remains, which date back to the early 1700s, were unearthed beneath a former parking lot. Long before that, the site had served as the First Baptist Church Burial Ground. While the cemetery was supposedly relocated in 1860, it seems, as CBS says, “that someone didn’t do their job.”

Among the dead are men, women, and children, but without headstones, their identities are not immediately apparent. Many of the coffins are falling apart with age, and local historians and archaeologists are ensuring that the remains are given the requisite care and respect. Efforts are underway to identify the deceased, and to figure out if they have any surviving descendants. Once the research is complete, the bodies will be reburied in Mount Moriah Cemetery.

The apartment building that is set to be erected on the site will be 10 stories tall, with 116 units. These will likely feature a number of modern amenities, as well as ghosts.