Hospital waste dating back almost 20 years has been found on a 120-acre site in north Co Dublin.
The illegally dumped waste, which includes patient records as well as hazardous materials including syringes, blood samples, theatre waste and surgical blades, dates back to 1982.
Industrial waste from a number of companies, including State-owned companies located near Dublin airport, was also uncovered in the find. It too dates back to 1982.
An initial find was made during pipe-laying in the summer at the perimeter of the site, which is owned by the IDA.
However, the IDA embarked on a more extensive investigation last month, uncovering further hazardous material.
This investigation was "ongoing", said Mr Colm Donlon of the IDA, "so the full extent of the amount of waste is not known yet".
He said the clinical waste was from hospitals on the northside of the city, though it was " too early to say which hospitals are involved".
Fingal County Council, the Health and Safety Authority, independent consultants as well as the Environmental Protection Agency had been advised of the find.
The site is situated between the M1 and the Malahide Road, at the end of the M50. It is near the residential centres of Darndale and Belcamp as well as Malahide.
The IDA bought the site - which comprised five farms and a GAA club grounds - in 1997 as part of a 10-year strategy to establish a high-tech industrial development centre in the area.
None of the waste was found on the GAA ground site. However the five farmers from whom the farms were bought would be would be spoken to in the course of the investigation, said Mr Donlon. This find represents the oldest illegally dumped hospital material discovered, following a series of such finds in Co Wicklow.
Following the find the IDA has withdrawn its complete planning application for the site which had envisaged the eventual provision of "between 6,000 and 10,000 jobs", continued Mr Donlon.
There was now a "question mark over whether the site would be viable for industrial development", he said, given the fact that "public liability insurance [was] impossible if there has been any pollution on a site".
Mr Adrian Conway, manager of Dublin Corporation's North Fringe Sewerage Project, whose contractor made the initial find, said the "suspect material" had been uncovered in the "upper layers" of the soil.
On specialist advice the sewerage pipe had been laid as planned, below the waste, he said. The waste had been put back where it was found and covered over until a decision is made on what should be done with it.
The affected area has been fenced off.
A spokeswoman for the EPA said the authority would become involved if a licence was needed to remove and treat the waste, while a spokeswoman for Fingal County Council said the matter was "mainly one for the IDA", though due to "the serious environmental risk", council personnel had visited the site.
Although IDA staff were now "bogged down" in "sorting this out", Mr Donlon said the main issue for the authority was how the find underlined the "lack of leadership and local management of waste".
Wicklow County Council is currently investigating more than 100 illegal dumping sites throughout the county.
