On Friday, the prefecture of the Maine-et-Loire received test results showing that the river contains algae cyanobacteria; toxic bacteria that can kill dogs or other animals swimming in or drinking from it.

The tests were carried out after eight dogs in the area perished following time in the water, reported French news source 20 Minutes.

The bacteria - specifically the oscillatoria and formidium types - is said to come from algae that forms on rocks and gravel in the river.

The bacteria often comes to the surface following periods of high rainfall, forming black-coloured clusters in the water, which are especially prevalent at the moment in the Loire, according to the statement from the prefecture.

Eight dogs - in the Montjean-sur-Loire, Saint-Saturnin-sur-Loire, Mûrs-Erigné, Saint-Jean-des-Mauvrets, Le Thoureil and Saumur areas - succumbed to respiratory and neurological problems after bathing and drinking water from the river, the report said.  

The prefecture has since “called for vigilance”, having received 12 reports of intoxication so far.

It has warned people not to allow pets to walk near to, bathe in, or drink from the river water, and has advised people to not drink the water themselves, eat any fish caught from the river, or pick up objects - such as wood or stones - that could have been submerged.

The advice holds for the Loire river, but also for any deep water that appears to have “high levels of algae or any [surface] mousse”, the statement read.

In early August, the region of Cher also reported a similar issue, but assured people that no animal deaths had been reported there.