An explosion followed by a fire killed at least one person and injured four at a French nuclear power plant Monday, authorities said.

The explosion occurred just before noon in a plant at the Marcoule nuclear complex in the Rhone Valley, near the southern city of Nimes. It is run by a subsidiary of EDF, the national electricity provider.

A local official told French media there was a risk of a radioactive leak from the facility, but a nuclear energy commission spokesman said no leaks had been detected ''for the moment,'' even as the fire continued.

A spokeswoman for the utility said the blast took place in a waste processing incinerator with a low level of radioactivity. Authorities established a security perimeter around the site.

The International Atomic Energy Agency activated its emergency centre in response. ''This is a very early phase,'' IAEA chief Yukiya Amano said.

France relies on nuclear power for more of its energy than any other country.

Prime Minister Francois Fillon called for an ''open and transparent'' audit of all 58 nuclear installations following the Fukushima disaster in Japan. The complete audit is expected in late September.