The gas supply has been fully restored to customers in Galway and Mayo this evening, according to Gas Networks Ireland.
"All customers in counties Galway and Mayo can now use gas safely," said GNI in a statement.
The Commission for Energy Regulation (CER), the independent energy safety regulator, has said it will carry out a full investigation into the cause of a technical fault that resulted in odourless gas entering the network from the Corrib Gas processing terminal in north Mayo.
GNI advised that customers should ensure all appliances are switched off prior to turning gas supply back on.
Further instructions on how to do this are available here.
"Gas Networks Ireland is cooperating with the Commission for Energy Regulation as they conduct an investigation into this incident," said GNI.
"Gas Networks Ireland would like to apologise to our customers for any inconvenience caused and thank them for the patience they have shown," added the statement.
Earlier, the Minister for Rural and Community Development called for the CER investigation to be carried out immediately.
"I welcome this investigation and I call for it to be commenced without delay. People in Mayo and Galway deserve an explanation of how this was allowed to happen and of the actions to be taken to ensure it cannot happen again," said Mr Ring.
"This investigation should be carried out and its findings communicated as a matter of priority.
"People in Mayo and Galway require certainty that the gas entering their homes every day is safe to use," he said.
Supply had been disrupted in Galway city, Salthill, Oranmore, Claregalway, Tuam, Headford, Westport, Claremorris, Crossmolina, Ballinrobe, Castlebar and Ballina.