Paris prosecutors said on Tuesday that cyber criminals had targeted the institution’s central computer system, but the incident had not caused any disruption to Olympic events taking place in the iconic glass-roofed exhibition hall in the center of the French capital.

The computer system at the venue also handles data for 40 mainly small museums with which it is affiliated, the prosecutors said in an email.

Franceinfo radio said the attackers had demanded payment of a ransom within 48 hours, threatening to post online the financial data they had obtained if they did not receive the unspecified sum of money.

France’s museums organization “Réunion des musées nationaux - Grand Palais” said in a statement it had asked national cyber security agency ANSSI to investigate the situation and that no data extraction had been detected.

It added that there had been no impact on operations at the Grand Palais, where Olympic events went ahead without a hitch and that the 36 museums it manages remain open to the public as usual.

At the end of July, just days before the start of the Olympics, French Prime Minister Gabriel Attal had revealed that nearly 70 cyberattacks linked to the Games had been foiled by French authorities.