Two people have been injured in an accident at France's oldest nuclear reactor.
Power company EDF denied reports of a fire at the Fessenheim plant in eastern France. The workers were apparently caught in an escape of steam.
The company said the incident occurred during routine maintenance.
Six others were reportedly slightly injured and local authorities said the incident was "the beginning of a fire."
Anti-nuclear campaigners have long pushed for the closure of the Fessenheim plant and warned of safety risks. France relies on nuclear energy more than any other country for its electricity needs.
Safety authorities said there was no threat of radioactive leaks and that the incident appeared minor.
EDF said that the incident occurred during routine maintenance and that smoke was released. It said two workers suffered slight burns on their hands after oxygenated water escaped during maintenance, and the workers received immediate medical treatment. All nine workers at the site were examined, it said.
Workers were treating materials in an annex of the plant, not the building that houses the reactor, when the incident occurred, said Thierry Charles, deputy director of the Institute for Radioactive Protection and Nuclear Security. He said they were preparing a chemical solution for cleaning purposes, and there was an unexpected chemical reaction that resulted in a burst of oxygenated water escaping.
"It has nothing to do with radioactivity," he said, noting that oxygenated water is widely used for industrial purposes. He said at this stage he sees "no risks" resulting from the incident.