FRANKFURT (Reuters) - Prosecutors on Tuesday raided offices of Germany's Commerzbank <CBKG.DE> as part of a broader investigation into a fraudulent share-trading scheme, the Cologne public prosecutor's office said.
A Commerzbank spokesman said that the bank could not comment on ongoing investigations.
"We are fully cooperating with the authorities and hope the matter is resolved as quickly as possible," he added.
The investigations focus on a practice, known as cum-ex, which involves cross-border trading of company shares around a syndicate of banks, investors and hedge funds to create the impression of numerous owners, with each entitled to a tax rebate.
The investigation into the scheme began as far back as 2013. Prosecutors have said the practice misled the German government into paying tax refunds that have cost the country more than 5 billion euros (4.47 billion pounds).
Earlier this month the first trial began as part of a wider investigation into the scheme, aimed at recovering billions from banks who profited.
Handelsblatt first reported the raids.
(Reporting by Arno Schuetze in Frankfurt and Matthias Inverardi in Duesseldorf; Editing by Thomas Seythal)