The Royal Berkshire Hospital has declared a major incident and been forced to close its A&E department after fire and flooding caused a huge power cut.
The hospital in Berkshire closed its A&E department to all patients except those with life-threatening injuries or conditions following an "isolated fire" in an electrical cupboard and a flood in a basement cause by a burst underground pipe.
Staff at the hospital worked throughout the night to restore power, but some areas are still affected by the outage due to water damage.
Members of the public have been asked to either attend an urgent care centre, a walk-in centre or A&E at Wexham Park, Stoke Mandeville, Frimley or Basingstoke while Royal Berkshire Hospital deals with the power cut.
Mary Sherry, chief operating officer for Royal Berkshire NHS Foundation Trust, said: "Our staff have been working hard through the night to ensure areas impacted by yesterday's power outage and isolated fire are back to normal.
"All water has been restored across the hospital. We now have the majority of power back on in North Block. However, we continue to have power issues on the north side of Battle Block, due to the extent of water damage. Our engineers on site are doing all that they can to ensure full power is restored as quickly and as safely as possible.
"Patients from the Coronary Care Unit were moved to Lodden Ward because of the smoke from yesterday's isolated fire. These patients will remain on Lodden Ward until the area is ready for them to be returned safely.
"The hospital is currently in major incident status due to the uncertainty of when full power will be restored to Battle Block and North Block. To ensure patient safety, we will be moving patients from Battle Block to other areas of the hospital."
A South Central Ambulance Service spokesperson: "We are still conveying all patients in life-threatening conditions to Royal Berkshire Hospital, but all other patients will be conveyed to alternative local emergency departments."