Many of Three’s 2m customers in Ireland were left without mobile phone services on Easter Monday because of an outage in one of its data centres.
Customers were unable to make phone calls or send text messages yesterday.
The mobile network became the second-largest mobile operator in Ireland after acquiring O2 from Telefonica for more than €850m last year.
It is understood that an electrical failure in one of the company’s data centres caused temperatures to rise and, as a result, systems came offline.
Engineers were understood to be working on the problem late into last night.
The outage had a ripple effect, affecting customers of Tesco Mobile, which uses the same network on an MVNO basis.
Three tweeted concerned customers this morning to let them know that the issue had been resolved and services were coming back on stream.