The French government and nuclear authorities on Monday moved quickly to staunch fears over the fallout from a blast, at a nuclear waste processing centre near Marcoule in southern France, which killed one person and injured four, DPA reported.
The Nuclear Safety Authority (ASN) said an incinerator at the site, which destroys metal objects of a low level of radioactivity, had blown up but assured there had been no leak of radioactive material.
"This accident bears no radiological risk nor (need for) action to protect populations," the authority said in a statement.
The building housing the incinerator had not been damaged and none of the four injured, one of whom suffered serious burns, had been contaminated, ASN said.
Tests carried out outside the building by the operator of the centre and the emergency services "revealed no contamination," the nuclear watchdog said, declaring the incident "over" by Monday evening.
The operator of the facility, the government and state electricity supplier EDF, which manages the adjacent Marcoule nuclear site, also assured there had been no contamination.
A security perimeter had been set up around the site, but the employees were not evacuated.
The facility is run by Socodei, a subsidiary of EDF, which specializes in the treatment of low-level radioactive waste. The centre is situated in Condolet, near Marcoule, one of France's oldest nuclear sites.
A spokesman for the company, speaking to television reporters at the site, called it a level-one nuclear accident - the lowest level on a scale of seven - and assured there were "absolutely no consequences" in terms of public health.
The badly injured worker was being transferred to a hospital in the city of Montpellier, he said.
The cause of the blast was still unclear. "The analysis of what happened has yet to be done," the spokesman said.
The nearby Marcoule site houses several decommissioned reactors, some of which used to produce plutonium for use in France's weapons programme.
In March, the site, which has been proposed to host a new-generation European Pressurized Water Reactor (EPR), experienced a level-two incident.
Immediately after Monday's accident the ASN activated its emergency centre in Paris.
The chief of the International Atomic Energy Agency, Yukiya Amano, said that the IAEA had also immediately activated its centre for nuclear emergencies and was in contact with French authorities.
France gets 75 per cent of its nuclear power from 58 nuclear reactors. Since the March earthquake and nuclear crisis in Japan, France has repeatedly said that its nuclear sites operate to the highest security standards.
Anti-nuclear activists are sceptical about France's transparency on nuclear issues, however, after France downplayed the risk of fallout from the Chernobyl disaster in 1986.
The leader of France's Europe Ecology/Greens party, Cecile Duflot, on Monday demanded "the greatest real time transparency on the situation and the environmental and health consequences."
Greenpeace said the fact that the site was not included in the audit of nuclear sites demanded by the government in the wake of the Japan disaster "again shows that France hasn't learnt the lessons of Fukushima."