Some commuters in a cosmopolitan European city may be shocked to learn they’ve been walking over ancient skeletons for many years. Officials in Brussels, Belgium, announced on April 9 that public works projects have led to the discovery of at least 30 skeletons in the heart of the city – and there may be more still to come. The archaeological excavation began when workers recently stumbled across the skeletons while working on tram tracks. Pictures show sharply dressed locals walking about the charming European city as excavators dig deep into a pit full of skeletons. Ans Persoons, secretary of state for Brussels, shared details about the excavation in an April 9 Facebook post written in both Dutch and French. Persoons identified the mass grave as the remnants of the old Saint-Jean Hospital, established in 1195. “Thanks to preventive excavations, 30 skeletons have already been cleared,” the translated post read. “It’s hard to imagine, but so many traces of our history are hidden under the pavements of Brussels!” The excavation is being conducted with the help of the Brussels Intercommunal Transport Company (MVIB) and workers from the city’s public water operator VIVAQUA. In a video posted by the MVIB, the agency wrote that the “centuries-old cemetery” was found while employees worked on the tram tracks in the Regentstraat, in central Brussels. “Between the 14th and 18th centuries, [the cemetery] offered the final resting place to the sick and local residents,” read the post, translated from Dutch to English. “Archaeologists are at work right now and hope to better understand everyday life in old Brussels through the excavations,” the agency added. The find is one of many European mass graves discovered in the past several months. Last summer, 50 “exceptionally well-preserved” Viking skeletons were discovered by archaeologists in Denmark. More recently, the Vienna Museum discovered the skeletons of more than 129 Roman and Germanic soldiers. Found under a soccer field, the mass grave dates back to the first century A.D. Fox News Digital’s Kyle Schmidbauer contributed to this report.