A nuclear plant in northern France was temporarily shut down on Monday after a swarm of jellyfish clogged pumps used to cool the reactors, energy group EDF said.

Four reactors at France's Gravelines nuclear power plant were shut down late Sunday due to a swarm of jellyfish in the cooling systems, operator EDF said on Monday, likely due to rising water temperatures because of global warming.

Four of the plant’s reactors shut down after swarms of jellyfish clogged its pumping stations. It isn’t the first time the creatures have thwarted nuclear plants.