Eva Kaili, the MEP suspected of accepting large sums of money to lobby in favour of Qatar, is expected to appear before a judge on Wednesday morning for a pre-trial hearing in Brussels.
Her title as European Parliament vice president was revoked on Tuesday by her own colleagues, in an overwhelming show of repudiation with 625 votes in favour and just one against.
She was one of several people arrested following a "major investigation" into criminal organisation, corruption and money laundering.
Kaili's lawyer, Michalis Dimitrakopoulos, has told Greek media his client is innocent and has "nothing to do with bribery from Qatar."
The Belgian judge will also question Kaili's partner, Francesco Giorgi, and former Italian MEP Pier Antonio Panzeri, Belgian media Le Soir has reported, as well as an unnamed NGO director, whom Italian media have identified as Niccolò Figà-Talamanca, secretary-general of No Peace Without Justice.
A decision is expected to be issued in the afternoon at the end of the hearing, which is set to begin at 11:40 am CET.
Two other suspects detained by Belgian police have been released and will not take part in the session.
The press was not allowed inside the highly-expected hearing at the Palais de Justice, leaving reporters to gather outside the court.
Since Kaili's shocking arrest on Friday, in which she was reportedly caught in the act, Belgian police have conducted over 20 searches and seized more than €1.5 million in cash.
Police have also "frozen" the IT resources of ten members of the European Parliament staff in order to prevent the disappearance of key data that might be useful for the investigation.
Several parliamentary offices in both Brussels and Strasbourg, including Kaili's, remain sealed.
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