Human remains have been found by builders digging up the patio at sheltered housing in Hemel Hempstead.
After making the shocking discovery they alerted police who rushed to St Mary's House in George Street, Hemel Hempstead, on Thursday.
Police are making inquiries as to why the remains, which they said were "very old", were at the site.
The Abbeyfield Society, which runs the sheltered housing site, wrote in a letter to residents that the remains were "estimated to have been there many, many years", according to the Daily Mirror.
Building work has been paused to allow forensic teams to carry out investigations.
A spokesperson for Hertfordshire Constabulary said: "Police were called at 12.11pm on 3rd October to a property on George Street, Hemel Hempstead to reports human remains had been found during work taking place.
"Officers attended and are making a number of enquiries as to why the remains, which are very old, were found at the location."
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