The judge may then formally charge the 55-year-old Oxford professor over the allegations which emerged in the wake of the Harvey Weinstein scandal, a judicial source told AFP.
Ramadan, a Swiss citizen whose grandfather founded Egypt's Muslim Brotherhood movement, was taken into custody Wednesday as part of a preliminary enquiry in Paris into the rape and assault allegations.
A regular face on French television, he is the most prominent figure to be held in France over the sexual assault and harassment claims that have rippled around the world as a result of the “Me Too” campaign.
Ramadan has denied the separate accusations from the two women.
The first was made by Henda Ayari, a feminist activist who previously practised a conservative strain of Islam. She had described being raped in a book published in 2016, without naming her attacker.
But in October, she said she had decided to name Ramadan publicly as the alleged perpetrator as a result of the “Me Too” campaign, using the French hashtag “Balance Ton Porc” (Expose your pig).
She said Ramadan raped her in his hotel room, telling Le Parisien newspaper: “He choked me so hard that I thought I was going to die.”
She lodged a rape complaint against Ramadan on October 20.
Several days later an unidentified disabled woman, a Muslim convert, also accused the academic of violently raping her in a hotel room in the southeastern city of Lyon in 2009.
Vanity Fair magazine, which met the woman, said her lawsuit against Ramadan described “blows to the face and body, forced sodomy, rape with an object and various humiliations, including being dragged by the hair to the bathtub and urinated on.”
During three hours of testimony in Paris on Thursday, the woman — using the pseudonym “Christelle” — recounted her allegations to the judge in Ramadan's presence.
Rejecting her testimony, the scholar refused to sign the official summary of the account, sources close to the case said.
“Both sides maintained their positions,” one source said.
During three months of investigations since the allegations emerged, police have interviewed dozens of people close to both Ramadan and the two women, and examined email and social media exchanges between them.
In November, Oxford University said Ramadan was taking a leave of absence from his post as professor of contemporary Islamic studies, “by mutual agreement”.
He has also denied allegations in Swiss media of sexual misconduct against teenage girls in the 1980s and 1990s, denouncing them as “a campaign of lies launched by my adversaries”.
Lawyers for Ramadan, a married father of four, have accused Ayari of slander and suggested the women colluded to try to disgrace him.
As part of his defence he has presented investigators with Facebook conversations in which a woman identified as Ayari allegedly made explicit advances towards him in 2014, two years after the alleged rape.
The accusations have sparked heated online debate between supporters of Ramadan, who commands a following of more than two million fans on Facebook, and his opponents.
Ayari was placed under police protection in November after receiving death threats.
Ramadan continues to head the Islamic Institute for Ethical Training in France.