Zurich, Jan 20 (Agencies): Prosecutors in Switzerland have opened a new criminal investigation against a Swiss banker who claims to have handed WikiLeaks details of rich tax cheats.

Zurich chief prosecutor Peter Pellegrini says Rudolf Elmer was arrested for questioning late on Wednesday.

Pellegrini said in a statement that the new probe centres on Elmer's trip to London on Monday at which he gave two data CDs to WikiLeaks founder Julian Assange.

It is unclear if Elmer is still being detained or has been released again.

The arrest came shortly after Elmer was found guilty by a Zurich court yesterday of coercion and breaking Switzerland's strict bank secrecy laws in an earlier case. A judge sentenced him to a fine of over 6,000 Swiss francs (USD 6,260), payable if he offends again in the next two years.