The KwaZulu-Natal health department has sought expert advice to establish the reason for the disruption of oxygen supply at Durban's Prince Mshiyeni Memorial Hospital.
Provincial health spokesman Sebe Zwane said they had not yet established what the main cause of the problem was.
Zwane said the situation at the hospital was under control and there had been no further patient evacuation to other institutions.
Yesterday, the hospital urged relatives to take seriously ill patients to other hospitals.
"Experts are working on the situation and we hope it will be sorted out soon. We don't know what the problem is or where it emanated from. But we have oxygen in cylinders," she said.
Zwane said the hospital was operating as normal except the casualty, intensive care and neo-natal sections that were adversely affected. The cut-off in the main oxygen supply started at midnight on Tuesday.
"Only three patients were transferred to other institutions.
"Afrox has a tender to supply the hospital with oxygen, but it is not clear when last routine maintenance was carried out."
Zwane said an internal investigation would determine the cause of the problem. "If it is found that human error was the cause, those responsible will have to account."
She said patients needing emergency treatment and more oxygen would be transferred to other institutions.