UPDATE: "Industrial accident, not nuclear accident."

Breaking news this morning. This was a major decommissioning site for nuclear weapons:

One person has been killed and four injured, one seriously, by an explosion at the southern French nuclear plant of Marcoule.

There were no radioactive leaks after the blast, caused by a fire near a furnace in a radioactive waste storage site, a French nuclear official said.

A security perimeter has been set up because of the risk of leakage.

The plant produces MOX fuel, which recycles plutonium from nuclear weapons, but does not include reactors.

The explosion hit the plant at 1145 local time (0945 GMT).

"For the time being nothing has made it outside," said a spokesman for France's Atomic Energy Commission (CEA).