The High Dependency Unit at Daisy Hill Hospital had been placed in quarantine following a flu outbreak.
The Southern Trust confirmed the Unit had been closed but has since reopened this afternoon (Monday) following a number of procedures, including a deep clean.
Newry & Armagh MP Mickey Brady said the ward itself has been placed in quarantine.
“I have no doubt that this will compound the pressures that our hospital services and staff are presently under,” said Mr Brady.
“I have asked the Trust to confirm details of the shut down of the High Dependency Unit which caters for the most seriously ill patients and also as to how those patients needing such medical attention are now being catered for.”
A spokesperson for the Southern Trust said: “The High Dependency Unit at Daisy Hill Hospital has not been accepting new admissions due to cases of ‘flu in the Unit.
“Strict infection prevention and control measures were implemented to keep patients safe, including a deep clean, and the Unit has re-opened to admissions this afternoon.”