NI Water has advised the public to run their taps after quality issues affected areas in the city centre.
Businesses in the Upper Arthur Street area were said to be affected.
Engineers for the water company are working on flushing the system.
A spokesperson for NI Water said it was not known what the cause was.
They said: “NI Water are dealing with a localised water quality issue affecting some customers in Upper Arthur Street.
“Teams are carrying out a flushable exercise to clear the system, which should resolve the problem.”
NI Water stated: “Any customer experiencing discoloured water from their taps are advised to run the water until it runs clear. Further advice can be found on www.niwater.com or by phoning Waterline on 03457 440088.
“NI Water would like to thank customers for their patience while this issue is resolved.”
Belfast Telegraph Digital