Galway County Council is investigating two illegal "sludge lagoons" in the east and north of the county.
The lagoons are located at Ahascragh, near Ballinasloe in east Galway, and in the Kilkerrin area of north Galway, according to the council.
Council officials inspected the site near Ahascragh and judged that it was not causing any environmental hazard at present, the local authority said at the weekend.
However, it is an unauthorised facility, and the council says it will be taking action under the planning legislation
The second lagoon was identified in the Kilkerrin area, and is also the subject of an inspection by council officials.
Last week, sludge pits with human sewage were declared illegal by Roscommon County Council at Kilbegnet on the Galway-Roscommon border, and the landowner and lagoon operator were instructed to return the land to its former state and to remove the sludge to a permitted outlet or spread it as slurry in line with farming regulations.
The three lagoons, with a capacity of up to 450,000 gallons of sewage, were constructed to sell the sewage on for fertiliser.
An application for planning permission and a permit for the facility was submitted to Roscommon County Council late last year, but it was withdrawn when there were public objections. Gardaí are investigating the circumstances surrounding an incident at the location where an RTÉ cameraman was allegedly assaulted by two men, and a camera was thrown into the lagoon.
One of the three Roscommon lagoons is within yards of the Suck River Valley Way.