Kuzmichev, who had been held for questioning since Monday, was put under formal investigation over allegations of laundering of tax evasion proceeds, money laundering and concealed work, the source said.

A lawyer for Kuzmichev declined to comment.

While the financial prosecutor’s office had sought for Kuzmichev to be placed in pre-trial detention, he will be set free under judicial supervision, the source said.

Searches took place on Monday at Kuzmichev’s Paris home and in the Mediterranean Var region as part of the investigation.

Being placed under formal investigation in France does not imply guilt or necessarily lead to trial but shows judicial authorities consider there is enough to the case to proceed with the probe.

It can take years before such probes either go to trial or are shelved.

French customs agents last year seized the oligarch’s 27-metre (88.58-foot) yacht “La Petite Ourse”, as part of sanctions by the European Union for his ties to President Vladimir Putin.

The move sparked a legal battle between authorities and Kuzmichev, one of the co-founders of Russia’s Alfa Bank who sold his stakes after the war in Ukraine broke out.

Kuzmichev, who is worth $6.4 billion according to Forbes, also co-founded the international investment group LetterOne, which owns several telecoms groups, but left the firm’s board in March last year.

Kuzmichev was one of very few Russian tycoons who stayed in the West after Russia invaded Ukraine.