More holes have been found under south Belfast's Ravenhill Road.
NI Water workers are now making urgent repairs to a 65 metre length of the busy road after discovering more "voids" following the discovery of a giant hole under the road surface on Monday.
It is believed the problems centre on an old Victorian sewer.
A spokeswoman said: ‘"Urgent work to repair the void discovered while carrying out sewer replacement work on the Ravenhill Road is nearing completion.
"However, CCTV footage taken of the area has identified similar voids which will require the same type of repair work."
The 65m section of the Ravenhill Road will be closed until the work is completed "for safety reasons" and will be reduced on an ongoing basis as the work progresses.
Today, cars travelling into Belfast city centre have been diverted onto the Ormeau Road, at the Rosetta roundabout, while country-bound traffic has been diverted via the Ormeau Embankment.
"As always in these instances the safety of the travelling public is our number one priority and we will continue to work closely with our colleagues in Roads Service to ensure that inconvenience is kept to an absolute minimum," the spokeswoman added.
"We do, however, appreciate that this will still cause difficulties for motorists using this busy route and will therefore be working to complete this work as quickly as possible. This has to be balanced with the needs of local residents.
“NI Water is grateful to customers and commuters in the area for their patience and understanding while this urgent repair work is carried out."