Last Updated 10:45 a.m. ET
PARIS - An explosion at a nuclear waste site in southern France Monday killed one person, seriously burned another and slightly injured three others, France's nuclear safety body said.
The Nuclear Safety Authority said no radioactive leaks have been detected in the blast at 12:37 p.m. local time, at an oven in the Centraco nuclear site. The accident was under control within the hour, the agency said in a statement.
Centraco is located on the grounds of another nuclear site, Marcoule, in the Languedoc-Roussillon region near the Mediterranean Sea.
"According to initial information, the explosion happened in an oven used to melt radioactive metallic waste of little and very little radioactivity," the statement said. "There have been no leaks outside of the site."
Those injured were not contaminated with radiation, and the outside of the building that houses the oven showed no sign of damage or contamination either, the agency said in a separate statement.
Local media reports that firefighters have thrown a security cordon around the Centraco plant, which contains an incinerator that burns low-level contaminated waste. The plant is run by Socodei, a subsidiary of the French power company EDF.
Officials from EDF stressed that there was no nuclear reactor on the site and that no waste treated at the site of the explosion came from a reactor. EDF spokeswoman Carole Trivi said a fire broke out after the explosion, but it has since been brought under control.
The cause of the blast was not immediately known, and an investigation has been opened, Trivi said.
A separate statement from France's Nuclear and Alternative Energy Commissions added that the site of the explosion remains sealed and its ventilators were operating.
The Marcoule facility, located in Langedoc Roussillon, in southern France near the Mediterranean Sea, opened in the late 1950s but was decommissioned as a power generator in the 1990s. CBS News' Elaine Cobbe reports there are total of four reactors on site, three of which had been deactivated.
Trivi said the Centraco plant treats mostly waste from EDF's own power plants, as well as a small amount of material from hospitals or medical research labs.
Nothing comes from weapons manufacture, she said.
According to AREVA, one of the French Atomic Energy Commission's industrial partners at the site, the facility has been reconfigured since 1997 to process decommissioned nuclear materials and waste, and for temporary storage.
MOX (mixed oxide) fuel - a nuclear fuel generated from uranium and plutonium recycled from nuclear warheads - is also produced here.