Lumps of a white substance found on some Cornish beaches, blamed for the death of a dog, have been identified as non-toxic fat.
Authorities had advised surfers and swimmers to avoid entering the water after the substance washed up at Praa Sands, Porthcurno and Penzance promenade.
Concerns were heightened when a local vet reported that a dog had died and others had been made ill after licking or eating the waxy substance.
Following laboratory tests, the substance has been confirmed as a non-toxic, degraded, edible oil or fat. The Maritime and Coastguard Agency is trying to identify the source of the pollution.
Dr Femi Oshin, from Public Health England in Devon, Cornwall and Somerset, said: "It's reassuring that the substance has been found to be some kind of cooking oil. It has clearly turned rancid and that's why we've had reports of it smelling so bad.
"While not harmful to people, it's unpleasant, and we'd still advise people – and dog owners with their pets – to keep away from it."
Cornwall Council said the oil was not harmful to humans, but could still be dangerous for dogs if they ate a large amount of the substance.