France came under close regulatory scrutiny on Tuesday for its decision to provide a €570m loan guarantee to finance the construction of the first nuclear reactor in Europe since the Chernobyl catastrophe in 1986.

The European Commission said it had opened an in-depth investigation into a guarantee that helped Teollisuuden Voima, the Finnish electricity producer, buy equipment from Areva. The French nuclear group, together with German engineering group Siemens, won the contract to build a new nuclear reactor at Finland’s Olkiluoto plant.