There had been reports that a ceiling in the hospital had collapsed and Ward 20 was being evacuated.
Foyle MLA Pat Ramsey tweeted "Hearing that the ceiling, has collapsed on Ward 20 at Altnagelvin Hospital, patients are being evacuated, hope that no one is injured.”
But a spokesperson for the trust says "there has been no ceiling collapse and no evacuation".
They did confirm that there had been water penetration to the roof of ward 20 though and some patients in ward 20 had to be evacuated to ward 7 and the day care unit.
A spokesperson from the Western Health and Social Care Trust (Western Trust) said: "A number of patients have been transferred to the Day Case area and other wards within Altnagelvin Hospital following a water leak at Ward 20 this afternoon.
The reason for the leak is still being investigated.
Patients were transferred for their own comfort and safety whilst engineers worked to fix any damage within the Ward.
It is anticipated that the affected patients will return to Ward 20 later this evening."