French authorities have discovered enough undeclared plutonium to make five nuclear bombs at a nuclear facility south of the country.

The Cadarache research center had earlier stated it had 8 kg (17.6 lb) of plutonium slated for decommissioning; however, 22 kg (48.5 lb) of the substance was found at the location during an inspection, Deutsche Welle reported on Thursday.

The amount of plutonium found at the Cadarache research center, near Marseille, could be as high as 40 kg (88 lb), France's Atomic Energy Commission (CEA) said, AFP reported.

French President Nicolas Sarkozy has ordered a thorough investigation into the incident.

"We need to have some transparency in this matter because this is not normal," said the French junior environment minister, Chantal Jouanno.

France's nuclear safety watchdog, ASN, has ordered dismantling work at the facility be halted over worker safety fears.

The undeclared plutonium was discovered in June, but was not reported until Thursday.

French Ecology Minister Jean-Louis Borloo said he "profoundly regretted that there was a delay between the discovery of the stocks and the decision to report them."

Anti-nuclear activists have accused industry officials of having lost control of France's vast network of reactors, treatment plants and research facilities. France runs some 58 nuclear reactors and considers itself a world leader in developing atomic technology.

The nuclear scandal in France breaks at a time, when the major world powers have mounted pressure on Iran to halt its nuclear program.

France, which is a veto-wielding member of the UN Security Council, has adopted a harsh stance against Iran, accusing its nuclear program of serving military purposes — a charge that Tehran has repeatedly denied.

Iran's ambassador to the International Atomic Energy Agency, the IAEA, had earlier declared that the US, Britain, and France are deceiving the international community over their nuclear programs.

"Those three countries in fact have violated for the last 40 years NPT articles," Ali-Asghar Soltaniyeh said in an interview with Press TV in September.

MGH/SS/MMN