An NHS Trust has declared a "major incident" after experiencing an unexpected power interruption.
East Surrey Hospital was identified as the location facing the disruption.
The hospital is closed to new attendances to the Emergency Department.
However, Surrey and Sussex Healthcare NHS Trust confirmed the hospital is safe.
Some non-urgent operations and treatments were cancelled following the incident.
Patients whose appointments have been cancelled have been notified.
The public have been advised not to visit East Surrey Hospital and seek alternative care for urgent treatment either in minor injury units and Urgent Treatment centres.
Caterham MIU, Crawley UTC, Horsham MIU and East Grinstead MIU were all listed as alternative locations to receive treatment.
A spokesperson for Surrey and Sussex Healthcare NHS Trust said: “We are working closely with our system partners and are working to urgently resolve the unexpected power interruption at East Surrey Hospital.
To support us, we are asking members of the public to use other local alternatives to ED – including alternative local Emergency Departments and nearby treatment centres at Crawley, Caterham Dene, Horsham and East Grinstead if your condition is not life-threatening.”
