France’s election campaign commission says “a significant amount of data” has been leaked on social networks following a hacking attack allegedly suffered by centrist presidential candidate Emmanuel Macron, 36 hours before the nation votes Sunday in the crucial runoff against Marine Le Pen.

The commission said Saturday that leaked data apparently came from Macron’s “information systems and mail accounts from some of his campaign managers.”

In a statement released after a morning meeting, the watchdog said the leaked data had been “fraudulently” obtained and that fake news has probably been mingled with it.

The commission urged French media and citizens “not to relay” the leaked documents “in order not to alter the sincerity of the vote.”

French electoral laws impose a blackout Saturday and most of Sunday on any campaigning and media coverage seen as swaying the election.

Meanwhile voting for France’s next president started in some overseas territories Saturday.

The first French territory to vote was Saint-Pierre-et-Miquelon, an archipelago located near Newfoundland, where polling stations opened in the morning. Early voting in other French overseas territories and French embassies abroad would begin later.

The 44-hour legal blackout on campaigning began Friday at midnight and is due to last until Sunday at 8.00 p.m. when the last polling stations close on the mainland and the first pollsters’ projections and official partial results are expected.

Fears of hacking and campaign interference have simmered throughout France’s high-stakes, closely watched campaign – and boiled over Friday night as Macron’s team said it had been the victim of a “massive and coordinated” hack.

His political movement said the unidentified hackers accessed staffers’ personal and professional emails and leaked campaign finance material and contracts – as well as fake decoy documents – online.

The perpetrators remain unknown. While the hack is shaking up the already head-spinning campaign, it’s unclear whether the document dump would dent Macron’s large poll lead over Le Pen going into the vote.

After ditching France’s traditional left-right parties in a first-round election, voters are now choosing between Macron’s business-friendly, pro-European vision and Le Pen’s protectionist, closed-borders view that resonates with workers left behind by globalization.

The future of the European Union may hinge on the vote, also seen as a test for global populism.

The leak, which began just before the blackout descended at midnight, in theatrical timing befitting the dramatic campaign.

Slamming the hack as an effort to “seed doubt and disinformation” and destabilize the vote, Macron’s movement En Marche said it would “take all measures” to shed light on what happened.

The presidential campaign has been unusually bitter, with voters hurling eggs and flour, protesters clashing with police and the candidates insulting each other on national television – a reflection of the deep divisions and public disaffection with politics.

Le Pen, 48, has brought her far-right National Front party closer than ever to the French presidency, seizing on working-class voters’ growing frustration with globalization and immigration.

Even if she loses, she is likely to be a powerful opposition figure in the upcoming parliamentary election campaign.

“We changed everything,” win or lose, Le Pen said in an interview with The Associated Press on Friday. She claimed an “ideological victory” and said she could still win on Sunday.