EU anti-trust regulators have opened an investigation into the restructuring of the French state-owned nuclear reactor builder Areva, the European Commission said on Tuesday.

The probe will "determine whether the French state's contribution to the financing of the Areva group's restructuring gave the company an unfair advantage not available to its competitors within the meaning of the EU rules on state aid," a statement said.

Problem-prone Areva, which is 87-percent owned by the French state, has faced severe difficulties since 2011, when the Fukushima disaster in Japan called nuclear power generation into question across the world.

Areva's woes were compounded by construction problems affecting its first EPR reactor in Finland -- now expected to open nine years late in 2018 -- putting company finances deep into the red.

In addition, Areva's former CEO Anne Lauvergeon has been charged in a case linked to the company's disastrous 2007 purchase of a Canadian uranium mining firm.

In April, Paris notified the EU Commission of a massive restructuring plan to save the national champion that included a 4.0-billion-euro ($4.4-billion) injection from the public coffers.

The plan also includes a proposal to divest major units of the company, including Areva's reactor unit to French energy giant EDF and Japan's Mitsubishi Heavy Industries.

"Given the size and importance of the restructuring of Areva, the Commission has to carefully assess that the restructuring plan is sound and that the state aid does not unduly distort competition in the Single Market," said EU Competition Commissioner Margrethe Vestager in a statement.

"Our aim is to ensure a sustainable future for Areva without the need for further government support," she added.

EDF, also majority-owned by the French state, agreed in June 2015 to purchase up to 75 percent of Areva's reactor unit at a valuation of around 2.7 billion euros, with the deal expected to be finalised in 2017.

"We are confident about the strength of our case," a spokesperson for the French economy ministry told AFP.

The probe should be wrapped up in time to finalise the rescue as planned by early 2017, the ministry added.

Areva did not respond to a request to comment.

France sees nuclear energy as a key national industry and the government has been closely involved in talks to restructure the sector.

The French state has already poured in billions to keep Areva afloat and thousands of French workers on the payroll.

Areva is also involved in the mining of uranium, primarily in Niger, and its processing into nuclear fuel.

bur-arp/ri

AREVA

MITSUBISHI HEAVY INDUSTRIES

EDF - ELECTRICITE DE FRANCE