A hospital was forced to turn patients away as their oxygen system hit maximum capacity due to too many coronavirus patients.
Watford General Hospital declared a critical incident on Saturday and said they needed to 'reduce the demand' so they could continue to run safely.
Patients were urged to use other hospitals with A&E departments for emergencies.
Some existing patients were also moved out.
A spokeswoman for the West Hertfordshire Hospitals NHS Trust told Mirror Online: "We didn’t run out of oxygen but our system was running at maximum capacity and so we needed to reduce the demand and make some adjustments to ensure it could continue to run safely.
"The first and most important point is that we retained a safe level of oxygen throughout the incident.
"In order to ensure that our capacity was enough to meet the needs of our patients, we transferred some patients out to other hospitals and closed our doors to new admissions."
The NHS trust chief responsible for the hospital, Christine Allen reportedly told the Metro similar incidents could happen again amid the Covid-19 outbreak.
On Saturday, Watford General Hospital said it had shut because of an "issue relating to the hospital's oxygen equipment" - but confirmed that it remained safe for its current patients.
It also confirmed it had not run out of oxygen despite reports suggesting this was the case.
The hospital closed to all patients except women in labour - and it was confirmed that a number of patients were transferred to other hospitals.
An official statement from the NHS trust on Saturday said: “As a result of a technical issue with our individual hospital’s oxygen equipment, which does not pose any risk to our patients, West Herts Hospitals NHS Trust declared a critical incident on Saturday April 4 and has asked that people do not attend Watford General Hospital.
“A small number of patients are being transferred to other hospitals in the area, with each patient being fully assessed in line with existing safety guidelines before they are moved.”
