German prosecutors searched offices at Deutsche Bank's headquarters in Frankfurt on Wednesday as part of an investigation into alleged fraudulent tax transactions linked to the lender's Postbank unit years earlier.

The bank confirmed that Duesseldorf prosecutors were at its office in the city, and that the probe related to transactions at its Postbank division between 2008 and 2010.

"Deutsche Bank is being searched as a third party in this matter and we are cooperating fully," Deutsche Bank said, declining to comment further.

Duesseldorf ⁠prosecutors ⁠did not immediately respond to a request for comment.

A person familiar with the matter told Reuters the search involved so-called cum-cum trades, confirming German media reports.

Such schemes involved trading in stocks of German companies around dividend payout days, which authorities say amounted to tax fraud.

The transactions ⁠flourished during the financial crisis, and authorities estimated they stripped state coffers of billions. A years-long crackdown has since sought to claw ​back the money.

The alleged roles of German financial ​firms in cum-cum trades, as well as in related cum-ex deals, are likely to cost the ⁠industry ‌around 7 billion euros ($8 ‌billion), German financial watchdog BaFin said last ⁠week, citing a survey.

It ‌marks the third time that prosecutors are known to have searched ​Deutsche Bank this year. ⁠A case earlier this year related ⁠to money laundering, and a second last week ⁠was related to its ​retail bank.

Deutsche Bank bought up Postbank, with its millions of clients and roots in the country's postal system, in ⁠phases, starting ‌in 2008.

In ‌2023, Deutsche Bank's years-long technology integration process with Postbank ⁠caused glitches and service lapses, resulting in ‌scrutiny by its regulator. A year later, legal issues over Deutsche's takeover of Postbank ​pushed the bank to post a loss, ⁠breaking a long profit streak.

Ten former managers at Postbank have been named as suspects, with damages of 350 million euros to ⁠the German state coffers, Sueddeutsche Zeitung ​reported.