Traffic diversions are in place on Kilmore Road this evening to allow repairs to an area which gave way this afternoon.
The area was between Dunmore Gardens and The Meadows, where new housing is being developed as part of the Knocknaheeny Regeneration project.
Local Fianna Fail councillor Tony Fitzgerald said the issue arose during work on a sewer this afternoon.
The area has to be reinforced and there is currently no access to Kilmore Road.
Cllr Fitzgerald said: "Irish Water are trying to resolve the issue."