Diesel spill inquiry continues at Aberystwyth harbour
An investigation is continuing into how red diesel got into the water at Aberystwyth harbour over the weekend.
The oil is causing an odour problem in the area but public health officials say it is not harmful.
The Environment Agency say the oil spill entered the water via the town's surface water drains.
Ceredigion council is advising people not to swim or surf in the area whilst the oil disperses.
Ged Davies, who is co-ordinating the Environment Agency's response to the spill, said the agency were notified of a problem by the Aberystwyth harbour master on Saturday morning.
He said that since then the agency had been assessing the impact of the pollution.
"Public Health Wales advised us that whilst the odour is unpleasant it isn't harmful to health, but Ceredigion Council has posted signs advising people not to bathe or surf while the oil disperses," he told BBC Wales.
Mr Davies added that it was "proving difficult" to minimise the pollution because while there was enough to cause a smell, there was not enough to mechanically or physically remove it.
"We can't stop-up the town's drains but we have specialist contractors on site to see if we can, in effect, filter the oil out from the rain water as it drains from the town," he added.
He added the agency was still trying to find the source of the pollution.
"You don't lose this amount of oil and not know about it, and if anyone is aware of some mishap occurring in the town we'd like to hear from them," he added.
The agency will also be contacting Customs and Excise later on to see whether it was possible to use an ultraviolet method to trace the oil through the drains, he said.
When the source is found anyone responsible may get a bill for the investigation and clean-up, he added.
No wildlife casualties have yet been reported, but Mr Davies urged anyone who came across any oiled bird to contact the agency.
"We can implement a plan we've got... to take the necessary measures," he added.