Patients were evacuated and the A&E has been closed until further notice after an electrical fire broke out at Aintree University Hospital.
Merseyside Fire and Rescue raced to the scene at around 4.34am today.
Six fire engines are at the scene.
The fire is said to have started on the roof of a three-storey building next to the A&E department.
Patients were seen outside in beds before the hospital fully reopened at 8.30pm.
Staff working at the hospital said that it smelled like "burning rubber" when the fire broke out.
A spokesperson for the hospital has now confirmed that people must seek "alternative treatment" for urgent and emergency care.
Security staff at the hospital told the Liverpool ECHO that A&E was evacuated along with some other departments on the first two levels of the hospital.
They said this was done as a precaution. They described the evacuation as "slick."
Emergency services have said some treatment rooms are now safe to go back into, with certain patients being allowed entry.
A cordon still remains in place, however, with firefighters and police at the scene monitoring the situation.
Traffic was diverted away from the hospital as crews worked to put out the fire.
Merseyside Fire & Rescue Service Area Manager Ged Sheridan told the ECHO that damage had been contained to the plant room, but he did expect there to be infrastructural damage.
He said: "The fire has been contained so the next step is full investigation into the cause of the fire.
"We’re ventilating and working on a multi-agency point of view on the hospital site to ensure that all of the areas can be fit for use following a clinical assessment and the site can operate safely.
“In terms of damage, it is contained to the plant room and to the battery compartment that seems to be the area of focus. Thankfully the fire did not spread - that was down to the quick actions of the firefighting crews and the actions of the staff.
"In terms of a significant area of damage to the hospital, it is minimal. There’s going to be infrastructural damage in terms of cabling, and power supplies and that’s to the estate staff to look at and investigate now. They’ll look at the full impact of the fire and any remedial action that needs to be taken today.”
Dr Jim Gardner, medical director at Liverpool University Hospitals NHS Foundation Trust, which runs Aintree University Hospital, said: “I’m pleased to confirm that the A&E Department at Aintree University Hospital has fully reopened from 8.30pm this evening.
“I’d like to thank our teams at Aintree Hospital and colleagues from Merseyside Fire and Rescue and Merseyside Police, whose calm and professional response in the early hours of this morning ensured no patients were harmed and the fire was contained.
“I’d also like to express sincere thanks to colleagues at North West Ambulance Service and at neighbouring hospitals and healthcare facilities for their support today while our A&E department has been closed and patients have been diverted elsewhere.
"The impact has been felt across local health services and this will have presented additional challenges to already pressured organisations.
“Finally, I’d like to acknowledge the support we have received today from the people we serve - our local communities - which has been hugely valued by us all.”
