PARIS (Reuters) – Pavel Durov, billionaire founder and CEO of messaging app Telegram, was arrested at Bourget airport outside Paris on Saturday evening, TF1 TV and BFM TV reported, citing unnamed sources.

Durov travelled aboard his private jet, TF1 reported on its website, adding that an arrest warrant had been issued against him in France as part of preliminary police investigations.

Both TF1 and BFM said the investigation focused on the lack of moderators on Telegram and that police believed this situation allowed criminal activity on the messaging app to continue unhindered.

Telegram did not immediately respond to a Reuters request for comment. The French Interior Ministry and police did not comment.

TF1 said Durov arrived from Azerbaijan and was arrested at around 8pm (18:00 GMT).

Telegram, based in Dubai, was founded by Russian-born Durov, who left Russia in 2014 after refusing to comply with demands to close opposition communities on his social media platform VK, which he later sold.

Durov, whose fortune is estimated at $15.5 billion by Forbes, said some governments have tried to put pressure on him, but the app, which now has 900 million active users, should remain a “neutral platform” and not a “player in geopolitics.”

(Reporting by Ingrid Melander and Gilles Guillaume in Paris and Lidia Kelly in Melbourne; Text by Ingrid Melander; Editing by David Gregorio)