An explosion occurred at French utility EDF's Flamanville nuclear plant on Thursday but there was no associated nuclear risk, a local government official said on Thursday.
A report in Ouest France newspaper said there may be some injuries. M6 radio said five people were slightly injured.
Officials at the state-backed company's Paris headquarters had no immediate comment and local officials at the plant in western France could not be immediately reached for comment.
The 1,300 MW each Flamanville 1 and 2 reactors were build in the 1980s. A new reactor is being built at the site but the explosion did not take place there, a spokeswoman said.
The nuclear safety authority ASN said it had no information and could not immediately comment.
Journalist Lisa Louis has more from Paris.