A Scottish health board has apologised after a malware attack meant appointments and procedures had to be cancelled.
NHS Lanarkshire also warned patients not to attend hospital unless their visit is “essential” and said waiting times may be longer than usual.
But the board’s chief executive, Calum Campbell, said the source of the malware had now been indentified.
Investigations are ongoing into how the malware was able to infect the network.
It was not clear if the health service had been deliberately targeted.
The cyber attack started on Friday. Operations were cancelled and the work of GPs was disrupted.
The health board said it “took immediate action” to put a solution in place and minimise disruption.
On Saturday morning, NHS Lanarkshire confirmed the problems were still affecting its staff bank system, which it uses to ensure shifts are filled on wards and clinics.
It asked staff to call a temporary number to check if they were needed to cover shifts over the next 72 hours.
Mr Campbell said staff had been working hard to minimise the impact on patients and contingency plans had been put in place to ensure services could be delivered while the IT issues were resolved.
“Unfortunately a small number of procedures and appointments have been cancelled as a result of the incident,” he said.
“I would like to apologise to anyone who has been affected by this disruption, however I can assure you that work is already underway to reappoint patients.”
“The majority of services have been restored but it may take some time to get services running as normal.
“We would ask patients who are attending hospital or out-of-hours services over the weekend to bear with us as they may experience longer than waits than usual.”
NHS Lanarkshire was one of the worst-hit health authorities in Scotland in the widespread cyber-attacks in May.
However, a spokeswoman for the health board said the current issues were “not on the same scale”.
She said a number of appointments and procedures had been postponed as a result of the current issues, but there were “no concerns around emergency treatments”.
NHS Lanarkshire’s hospitals include Monklands, Wishaw General and Hairmyres.