Oil leaks into Aberystwyth harbour
An investigation is under way after oil leaked into Aberystwyth harbour.
People staying on boats have been advised to find alternative accommodation because of the odour, while affected residents have been asked to shut their windows.
The Environment Agency believes the oil entered through the sewage system, but the leak has been stopped and there is no threat to the environment.
Public Health Wales said the odour was unpleasant, but was not harmful.
The agency said it would monitor the situation, although it expected the spill to disperse naturally.
Ceredigion council has posted notices locally to alert people of the spill.
The Environment Agency said people experienced any health problems should seek advice from their GP or contact NHS Direct Wales on 0845 46 47.