Eircom has said it cannot say when a major phones problem which has affected hundreds of thousands of people will be fixed.
Mobile and landline services for some businesses which use 1800 and 1500 numbers - as well as ISDN lines - have been down since just after 10am today.
Eircom said they had not yet identified the cause of the intermittent problem and technicians were working to resolve it.
Dublin Fire Brigade has tweeted to say it has been advised by Eircom that using landlines to contact emergency services may be difficult.
We are advised by #eircom that using landlines to contact emerg servs may be difficult. Some mobiles also affected. This is a national issue— Dublin Fire Brigade (@DubFireBrigade) September 2, 2015
Assistant chief fire officer with Dublin Fire Brigade Denis Keely said: "The first point of contact is from their mobile phone or from their housephone because it is an intermittent issue. Our understanding is the 112 and 999 numbers are ok."
Childline has also tweeted that children trying to use its service may be experiencing problems.
Important!! Children trying to contact #Childline number might experience problems due to Eircom issue. Go to Childline.ie for help. Pls RT— ISPCC Childline (@ISPCCChildline) September 2, 2015
Customers cannot call the Eircom customer care centres so are being advised to report the fault online.
Director of Corporate Affairs at Eircom Paul Bradley said: "We're working as hard as we can to identify the root cause and get the full service restored as quickly as possible (but) I can’t give an estimation as to when full service will be restored."
Gas Networks Ireland said it is aware of the eircom fault.
“This may affect customers using the 1850 20 50 50 number to report gas escapes,” it said in a statement.
“If you cannot get through on this number, please call one of our temporary gas emergency numbers.
“The following are the numbers; 087 9160734 or 087 9160701. These numbers are only to be used in case of a gas emergency. Alternatively, call 999 or 112.”