Barriers have protected swans from the area affected by the spill

Fifty gallons of red diesel oil entered a water lagoon in Abergele at about 1630 GMT on Wednesday.

A member of the public alerted Conwy Council to the spill and firefighters were called to contain the oil.

A barrier was placed across the lagoon in Pentremawr park to protect swans from moving onto the lake.

Officers from the Environment Agency visited the site on Thursday and are continuing to investigate the spill.

A council spokeswoman said staff were containing the fuel to ensure wildlife is not in danger.

"Officers will try to trace the source of the contamination, which will then make it possible for the clean-up to begin," she said.