VISITORS to Bournemouth's award-winning Pleasure Gardens became detectives after a mystery spillage contaminated the Bourne Stream.

A thin layer of an oily substance swirled in the water between the Square and the seafront, while a petrol-like smell lingered in the air at the Lower Gardens.

"You can really notice the smell when you go into the gardens, and the shine of the oil is very easy to see," said Kathleen Hooper, 77, from West Cliff.

"The water is always so clear, so the contamination is very noticeable," added husband Russell.

Tim Diss, 49, from Croydon said heating oil could have been responsible for the pollution.

"I don't think it is the sort of fuel you would get at a filling station - whatever is in the stream has a different smell," he said. "But you do not expect to see it in Bournemouth - the happiest town in the UK."

Holidaymakers Ann and Bill Broad from Kent added: "The gardens are beautiful, but whatever is polluting the stream has spoilt it."

An investigation into the spillage was launched on Friday afternoon following complaints that the stream had been polluted.

Cllr Bron Littlewood, Bournemouth Borough Council's environment, leisure and tourism portfolio holder, visited the gardens on Saturday morning to assess the problem herself.

"I can't see anywhere along the Lower Gardens where something could have leaked - the substance may have been dumped," she said.

"I hope that the Environment Agency will have results for us by Monday morning as we do not want the situation to get worse, but we also need to find out if there's a problem here somewhere."

There did not appear to be any contamination in the Higher Gardens, where ducks continued to swim in the stream.

Last year Wessex Water revealed that the eight mile (13km) long stream was cleaner than ever.