An incident at a closed nuclear power plant in eastern France generated a lot of smoke Thursday, but won't have an impact on the environment, officials said.

The smoke developed at the Superphoenix fast breeder reactor at Creys-Malville near the border with Switzerland in a room where sodium was stored, according to officials.

The incident was under control at 9:00 pm (1900 GMT), they said.

"The accident happened in the non-nuclear part of the site and there were no flames," plant director Veronique Bouilly told AFP by telephone.

The Rhone-Alpes regional nuclear watchdog said the incident would "not have any consequences".

The dismantlement of the Creys-Malville reactor is expected to be wound up by 2025, after the socialist government under then prime minister Lionel Jospin decided its closure in June 1997 for ecological reasons and excessive costs.