Residents of Ballyogan in south Co Dublin have called for a permanent halt to excavation work at a landfill in the area after Dún Laoghaire-Rathdown County Council revealed it has recently discovered medical waste there.
Among the items found by workers on the site, which is due to be converted to parkland, were syringes and needles which were mixed with clay and other general waste.
A spokesman for the council said it had stopped excavation on the site pending a full waste characterisation and risk assessment studies on the materials uncovered.
It believes the waste may have been deposited up to 20 years ago.
"There is a protocol in place for managing such materials, and we are following it closely," the council's senior engineer, Peter Goodwin, said.
"It will be some time before we are in a position to say exactly what is there, how much of it there is, and what is best practice for dealing with it. It is also too early to say where the waste came from."
The Environmental Protection Agency (EPA) will be on site this week to assess the materials.
The materials will be tested over the coming weeks to determine their precise nature. The EPA will also be involved in determining how much medical waste is on site, and the extent of its spread.
The excavation project had been due to finish at the end of this month.
However, it is now likely to be delayed for a number of weeks pending the results of the EPA tests.
A spokeswoman for the council said it had been liaising with the community to ensure residents were kept up to date with developments at the site.
However, Nicola Curry, chairwoman of a Ballyogan environment group, claimed residents had been told there was no medical waste at the site.
The council has acknowledged that there is a "minimal" risk of odourless methane gas being released from the site.
Ms Curry called for work on the site to be halted permanently. Failing this, at the very least a full risk assessment of the site should be carried out to ascertain exactly what it is the council may be disturbing.
"They have insisted emphatically to us that there was no medical waste," she said last night.
"But we knew from previous pickets we mounted on the site years ago that there was medical waste deposited there."