The results are in, and the mysterious butter-like substance that appeared on parts of Whanganui's Castlecliff Beach last month has been identified.
Horizons Regional Council received a complaint about the wash-up via its pollution hotline at 9.45am on August 8, with a pollution response duty officer arriving at the Morgan St beach access about an hour later.
Horizons consents monitoring team leader Pita Kinaston said a sample had been taken and was analysed by an independent laboratory.
"It was found to have a high proportion of fats, oil and grease indicating that the source was likely from animal fats or another type of oil such as cooking oil," Kinaston said.
A Horizons pollution response duty officer conducted another survey of Castlecliff Beach at two sites - the end of Seafront Rd beach access and Rangiora St beach - on August 17, he said.