Two million customers in Ireland lost network over Easter Monday.
Overheating led to an electrical failure at one of Three’s data centres in Ireland bringing services down to as many as two million costumers.
The incident mainly affected users who were transferred from O2 after Three Networks acquired the company in 2014.
The fault was detected on Monday at 3pm and no calls or text messages could be sent or received by consumers across Ireland.
A Three spokesperson told the Independent.ie that "some customers experienced intermittent 2G and 3G service issues".
It continued: "This has occurred due to an electrical failure at one of our data centres which caused an increase in temperature in the building and then subsequently impacted some systems affecting customer service.
"Our dedicated Networks team is continuing to work hard to resolve this as soon as possible and we apologise for any inconvenience caused."
Tesco Mobile services were also affected by the electrical fault as it uses Three’s network to provide Irish costumers.
The official Three Ireland Twitter account said: "Some customers may be experiencing issues with their service. We’re working on getting this fixed ASAP. Sorry for any inconvenience caused.
"We’re aware that customers may be having service issues. Work to resolve this will continue tonight."
Services were back up this morning putting an end to over ten hours of network loss nationwide.