F1 driver turned commentator Mika Salo spent two days in custody at the end of last month, the Finnish newspaper Suomen Kuvalehti reports.
The report said the 46-year-old, who last raced in F1 for Toyota in 2002 and is now a pundit on Finnish television MTV3, is facing charges for tax fraud.
He was reportedly arrested at Helsinki-Vantaa airport after returning from the recent Singapore grand prix.
An official said: "The suspects deny committing any crime."
Salo would not comment.