France’s beaches have been inundated by lethal slime with what experts say has the potential to kill sunbathers within seconds.

Fears have heightened and six beaches were closed this summer in Brittany as the “killer slime” took over the vacation destination, the Guardian reported.

“It’s a shame this place has come to be associated with death,” said André Ollivro, an environmental activist who warned that large amounts of green algae on the beaches can “kill you in seconds.”

Piles of toxic algae have covered the shore on the northern coast near Saint-Brieuc due to the over-fertilization of nearby fields draining into the ocean, according to the news outlet.

The sludge, which releases poisonous hydrogen sulfide gases that can lead to loss of consciousness and cardiac arrest, has washed up on the shores for decades, but environmentalists say that the problem has worsened this summer due to “exceptional” weather, according to France 24.

“The influx of green algae began very early, there were few storms and June was a relatively wet month, which caused more water to flow from agricultural areas and thus more green algae,” a spokesperson for the Saint-Brieuc town hall told the outlet.

At least two people and dozens of animals have died from inhaling the toxic fumes in the area, though some warn the cases don’t reveal the full scope.

“Around 20 people die on the coast each year, often swept away with tides or currents, but the question is: could some of those people have fainted from toxic gas from seaweed before being swept out? The state has not shed full light on all these issues,” Inès Léraud, who penned an investigative comic book on the scandal, told the Guardian.