Hundreds of operations and appointments have been cancelled after a computer virus infected systems at three hospitals.
It comes after the trust which runs the hospitals declared a major incident after being advised to shut down the majority of systems to isolate and destroy the virus.
Northern Lincolnshire and Goole NHS Foundation Trust said all planned operations, outpatient appointments and diagnostic procedures would be cancelled today and tomorrow.
The trust said it would continue to look after inpatients and major trauma cases would be diverted to neighbouring hospitals as would high risk women in labour.
Medical director Lawrence Roberts said everything from systems to access patients records to pathology results and X-rays had been affected. He said: “It’s very worrying in a modern age when you take away someone’s ability to access software your ability to continue to function deteriorates very rapidly.
“We started getting unusual responses to software last night. Some of it wasn’t responding in the way we would expect it to.
“This morning it got worse and a series of cyber experts here and in the US have looked at the systems.
“They are absolutely sure we have a malicious virus in the system and have advised us the best way to remove it is to shut the systems down while the server is cleaned.”
The hospitals see approximately 1000 patients and outpatients a day, and carry out 50 to 100 operations.
The trust says it will review the situation on an hourly basis.
A statement added: “Our clinicians will continue to see, treat and operate on those patients who would be at significant clinical risk should their treatment be delayed.
“Further updates will be posted on the Trust website and social media channels.
“We would like to apologise to all patients who are affected.”