The liquid found close to the outfall outlet on Thursday had a bad smell of diesel and Environmental Health officers want local residents and businesses to check their oil tanks for leaks.
They don’t want any dogs or horses walking through the liquid or drinking it and have put up signs on the beach warning people to keep away from the area.
Officers are now working out whether any further action needs to be taken.
If you know anything about the spill you can call the pollution hotline on 709535 or email envprotection@gov.je