An explosion and fire have occurred at the Flamanville nuclear plant on France's northern coast but there was no nuclear risk, officials say, reports the BBC.
"It is a significant technical event but it is not a nuclear accident," senior local official Olivier Marmion told AFP news agency.
Five people reported feeling unwell but none was seriously injured.
Flamanville has two nuclear reactors. A third one under construction is the model for a new reactor in the UK.
The cause of the blast was not immediately known.
One of the older reactors was shut down after the blast which, according to Ouest-France newspaper, happened in a machine room at about 10:00 (09:00 GMT).
The incident was declared over at 11:00.