Authorities investigate mystery muck on Wanganui beach

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Authorities are trying to get to the bottom of how truckloads of a mystery substance containing wool have washed up on Wanganui's South Beach.

A large quantity of the brown substance washed up between Kaitoke Stream and South Mole on Sunday evening or Monday morning.

Got photos of the mystery muck? Email us here.

Wanganui Mayor, Annette Main, said there are two layers on the beach, indicating it washed up over two high tides.

She didn't know where the substance has come from, but confirmed it had nothing to do with the town's wastewater system.

The council has closed the beach and trucks will be brought in to start removing the muck today.

Test results should be back in a few days.