Planners have launched a probe following claims that a rare site where early humans settled has been badly damaged without carrying out proper archaeological investigation.
The Department of the Environment (DoE) said its planning department has launched an enforcement investigation to establish if a breach of planning control had taken place at Ballymaglaff in Dundonald in relation to archaeological matters.
Northern Ireland Environment Agency (NIEA) also sent staff to inspect the site after concerns were raised about the road access to a new housing development close to the Comber Greenway.
Local historian Peter Carr, who discovered the archaeological site in 1984, says it dates from the era of the first human settlement of Ireland, the early Mesolithic period 8,800-9,800 years ago, and more than 2,000 pieces of struck flint have been found there.
"Over 20 of the period's rare and highly distinctive microliths have been discovered here. Very few sites can claim over 10," he said. "The larger part of the site was destroyed in January during the building of an access road to a new housing development.
"Although the site is on the Department of the Environment's Sites and Monuments record, as a result of an administrative oversight no protective archaeological clause was attached to the planning permission.
"Archaeologists tested the area before construction work began, but the 'trial excavation' used the wrong archaeological methods and as a result nothing was found.
"The archaeological layer, which contained early Mesolithic flints and possibly other material, was left in spoil heaps near the road. These have not been protected and soil from the heaps has subsequently been redistributed."
However, DoE planners said they had placed archaeological conditions on the planning permission.
"The most recent planning permission was granted November 20, 2013 for housing and an access road. When assessing the application, DoE Planning consulted with the NIEA, who recommended conditions requesting a written scheme and programme of archaeological work to be prepared by a qualified archaeologist for approval by the department," a spokesman said.
"These conditions were placed on the planning approval. The applicant carried out a test evaluation of lands near the road. This was conducted under licence from NIEA. No archaeological material was identified during this evaluation.
"A meeting will take place next week with the department and the developer to discuss options."
Peter Woodman, Ireland's foremost expert on the early Mesolithic period, said few sites on the island have produced such numbers of microliths, which are pieces of blade that would have been inserted into wood or bone to create composite tools. He said: "You excavate for information. Bits and pieces of stone tools are one part of that, but there are other equally important things."
Excavation at Ballymaglaff could have yielded evidence of huts, post holes and fireplaces to help build a picture of how early humans lived in Ireland, he said.
"The destruction of a site about which so little is known is always a great tragedy," he said.
A spokesperson for Lagan Homes, which is developing the site, said: "Lagan Homes complied fully with – and exceeded – the archaeological conditions attached to these works. The company strongly refutes any suggestion that it did not comply with planning conditions."
Mr Carr insisted Ballymaglaff could still yield valuable information. "If the department gets its act together, material could still be salvaged from what remains of the heaps," he said.