Steel supplied by Kitakyushu manufacturer Japan Casting & Forging Corp. to nuclear facilities in France has been named in an investigation that found it had a high level of impurity, the nuclear watchdog said.

The Nuclear Regulation Authority said the standard for carbon content in metals — a gauge of impurity — is below 0.22 percent in France, while the figure is below 0.25 percent in Japan.

But in some products provided by Japan Casting & Forging Corp. for some nuclear facilities, carbon content in steel was over 0.3 percent.