What the machinery exposed in 1990 were two cists, a type of burial box made from stone slabs, lying close together beneath the mound. Their survival until that moment was, by any measure, a close-run thing.

A rescue excavation carried out in 1990 by the National Museum of Ireland recovered what remained. The larger of the two cists measured roughly 1.83 metres east to west and less than half a metre across, just large enough to contain a single body lying extended. It was built from long, thin slabs set upright on edge, seven in total across the two long sides, with the pit beneath lined in clay. Unusually, neither the east nor west end was closed with stone. Three capstones had slipped from their original positions and were found gathered at the eastern end. The western half of the interior was partly paved. Only two bones survived: an unidentifiable fragment, and a femur belonging to an adult, possibly male, lying on one of the paving slabs. The position of the femur indicated that the person had been placed with their head to the west, a orientation broadly consistent with early Christian burial practice. Radiocarbon dating of the bone returned a calibrated date of 545 to 664 AD, placing the burial firmly in the early medieval period. The second cist lay just 0.85 metres to the south-east, also beneath the mound. Whether either burial had any original connection to the mound itself, or whether the mound was already ancient when the cists were dug into it, remains uncertain.