A river described as one of France’s prettiest is now also its fattiest.

An industrial accident led to the 39-mile-long River Odet being polluted by a massive butter slick, The Local reported Wednesday.

Lumps of the smooth-sailing slick began to build up along the river’s banks after “hundreds of kilos” found their way into the water from the Beuralia dairy plant, Le Telegramme reports.

The dairy plant and firefighters are investigating the incident and have shut off a gate that allows water from the facility to flow into the river.

Beuralia is the second-largest butter manufacturer in France, The Local adds.

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