The Department of the Marine is investigating the source of an unidentified brown slick first reported earlier this month in Broadhaven Bay, Co Mayo.
Enterprise Energy Ireland (EEI) has denied claims it was the source of the pollution. A spokesman said the company had used dyes to examine currents in Broadhaven as part of environmental impact assessment work. This involved 1.5 pints of harmless vegetable oil, which was last applied in August.
The chairman of the Erris Inshore Fishermen's Association, Mr Eddie Diver, said that local people wanted answers as to where this slick, stretching for about two miles was coming from.
He described it as "brown stuff with a blue tinge, and of a spongy like substance".
A dead whale has also been washed up on the shoreline.
"We are calling for a post mortem, because we are aware that EEI are carrying out seismic tests along this shoreline," he added.
A spokesperson for Mayo County Council yesterday said it was investigating the slick and the source. The Department of the Marine said the slick had been first reported on September 5th.
Samples that were taken are still being examined, a spokesman said.