A major incident was declared at NHS hospitals across England and Wales on Wednesday (24 January) after mysterious IT failures hit two separate data centres.
The downtime left doctors and NHS staff unable to access patient records and reports indicated that email and intranet services were also been hit by the outages. The problems were ultimately resolved within 24 hours, but officials said the faults remain under investigation.
Two data centres, according to Welsh government, were located in Blaenavon and Cardiff Bay.
"This is under investigation by the NHS Wales Informatics Service (NWIS) and is being dealt with as a priority," a brief statement read.
The National Cyber Security Centre (NCSC), a fork of British intelligence agency GCHQ, said the incident was not believed to be the result of a cyberattack.
Wales' Department of Health and Social Services said that it was being "dealt with as a priority."
As reported by WalesOnline, Powys NHS IT department said: "There is currently a major incident affecting a number of nationally hosted systems across NHS Wales. The issue appears related to national firewalls and is being currently investigated by NWIS."
It noted that the system manages appointment systems, prescriptions and medical notes.
Describing the incident to the BBC, a GP called the situation "chaos". Another insider, Dr Alan Woodall, chairman of GP Survival UK, commented: "We are working emergencies only – in the middle of influenza/winter crisis this is a major impact if it continues."
Manchester Royal Infirmary and Royal Manchester Children's Hospital were also impacted, according to the Manchester Evening News.
"Please only attend A&E for serious or life threatening emergencies," tweeted Manchester University NHS Foundation Trust. A spokesperson added: "We are working to resolve this as quickly as possible and services are using their well-rehearsed business continuity plans."
Morlais Health, a Welsh GP surgery, tweeted Wednesday: "NHS IT systems are down across Wales, including at Prince Charles Hospital and in many GP practices including ours.
"We are still able to see emergency patients however we have no access to any medical notes, our appointments system, repeat prescriptions etc.
"If you have an appointment for an urgent issue then your appointment will be honoured but please bear with us as our ability to provide high quality care will be more limited today. NHS Wales Informatics Service (NWIS) are currently working hard to solve the problem.
"We apologise for any inconvenience caused but this matter is entirely out of our control."
The same day, NHS Digital announced that it had entered a new deal with tech giant Microsoft to support hospitals and better protect their IT infrastructure against cyberattacks.
Later in the evening, NHS Wales health IT tweeted: "Both NHS Wales National data centres are now back online following an earlier networking outage. All clinical systems are now available.
"NWIS will continue to monitor the situation and work with our equipment suppliers to investigate the root cause. We appreciate that this will have caused disruption to our users and we apologise for any inconvenience caused."
The Manchester University NHS Foundation Trust added: "Normal services resume. We would like to thank patients and our staff for their co-operation and support during this time."
This article was updated on Thursday (25 January) to confirm that issues had been resolved.