A large nuclear power plant in France was forced to shut down temporarily after a ''massive and unpredictable invasion'' of jellyfish broke into its cooling system.

On Sunday evening, four reactors at the Gravelines site in the north of the country shut down automatically after jellyfish infiltrated the filters of the pumping stations. The entire plant remained offline on Tuesday morning after the two remaining units were shut down for planned maintenance. EDF said the delays caused by the invasion are expected to last into the week.