France's financial prosecutor has opened a preliminary probe into state-controlled nuclear giant Areva's controversial 2007 purchase of a Canadian uranium miner, a judicial source said Thursday.

The probe focuses on the $2.5 billion (1.8 billion euro) purchase by Areva of UraMin at a height of demand for enriched uranium.

Areva was later forced to revalue its UraMin uranium mines to only 410 million euros.

Canadian media reports have suggested the sale was preceded by suspicious stock trades.

French newspaper Le Monde said France's Cour des Comptes, which oversees state accounts, had referred the case to prosecutors.

It said the Cour des Comptes is to release a report into Areva's 2006-2012 finances later this month.

Areva's chief from that period, Anne Lauvergeon, said in a statement Thursday that the deal was "strategic at the time", noting that it was "submitted and approved by the group's decision-making bodies".

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