A Belgian judge ruled on Thursday that European lawmaker Eva Kaili will remain in custody for another month as an investigations continue into corruption charges in a graft case involving World Cup host Qatar, Belgian prosecutors said. Kaili can appeal the decision within 24 hours.

Kaili is one of several people to have been arrested in the case.

She is accused of corruption, membership of a criminal organization and money laundering. Belgian police arrested her on December 9 after finding large sums of cash in her house. 

Her lawyers on Thursday said they requested her release and to be placed under electronic surveillance instead.

Kaili was "cooperating in an active manner" with the Belgian probe and she "rejects all corruption allegations against her," said Andre Risopoulos, one of her lawyers.

Michalis Dimitrakopoulos, another lawyer representing Kaili, said on Wednesday that she would not flee nor destroy evidence.

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What is the EU corruption scandal? 

Kaili, who has been removed from her position as one of the European Parliament's 14 vice presidents, is suspected of having received bribes from Qatar to sway policy. Doha has denied involvement. 

Kaili's partner Francesco Giorgi, the head of an NGO allegedly used to funnel money and a former MEP-turned-lobbyist were also charged. 

Belgian media reported earlier this week that Kaili had acknowledged partial guilt and allegedly admitted to having been part of a group that facilitated funneling bribes from Qatar and Morocco to MEPs .

Giorgi is said to have named former Italian MEP Pier Antonio Panzeri as being the head of the organization.

Panzeri was also arrested on December 9 and has since been in custody. Police discovered some €600,000 ($637,000) in cash in his apartment in Belgium.

Belgian police have raided several apartments and European Parliament offices as part of the probe. They seized around €1.5 million in cash.

The scandal is one of the largest in EU history. It has done incalculable damage to the bloc's reputation and invoked calls for reform in the European Parliament.