Germany says it wants France to shut down the Fessenheim nuclear plant near its border as soon as possible.

The demand follows German media reports that an incident at the facility in April 2014 was more serious than previous known.

A spokesman for Germany's environment ministry says the incident was discussed by a Franco-German nuclear safety panel at the time.

Stephan Haufe says Germany shares France's assessment about the seriousness of the incident — "one" on a scale from zero to seven — but remains concerned about the reactor's age. It began operation in 1977.

Haufe said Friday "it's not the first incident or the first problem that we know about from this reactor, and that's why the environment minister demands the reactor be shut down as soon as possible."