Beneath the stone floors of the over 500-year-old Bath Abbey church in England is a tangle of buried human bodies that are now threatening the long-term stability of the entire building. According to the BBC, up to 6,000 bodies may be buried beneath the church, which has existed in different forms on the same land since 757 CE. Though the burials stopped around 1840, until then, "they just jammed them in and jammed them in — it would have been very unpleasant to put it mildly," Charles Curnook, a representative of Bath Abbey, tells the BBC.

The bodies have created massive voids beneath the church that are causing its floors to collapse, Curnook says. "We were quite surprised the floor hadn't collapsed already on us." The bodies have been an issue for Bath Abbey in the past, and though they were dealt with, it never happened properly: "[The church] basically churned up the graves that were there and broke them up," Curnook tells the BBC.

Now, Bath Abbey is lifting its floors to fill in all of the remaining air gaps that could cause it to collapse. Already, the BBC reports that 10 cardboard boxes have been filled with human remains that were unearthed in the dig — the bodies will eventually be returned and prayed over, but only once the ground is stable. The renovation is finally coming to Bath Abbey as part of an £18 million (around $28 million) improvement project. There's no specific date on when work on the ground beneath the building will be complete, but it's estimated that the full project won't be finished until at least 2018.