Money laundering allegations linked to the "Panama Papers" led police in Germany to raid six Deutsche Bank offices in and around Frankfurt on Thursday.
Investigators were looking into the activities of two unnamed Deutsche Bank employees alleged to have helped clients set up offshore firms to launder money, the prosecutor's office said.
Around 170 police officers, prosecutors and tax inspectors searched the offices where written and electronic business documents were seized.
"Of course, we will cooperate closely with the public prosecutor's office in Frankfurt, as it is in our interest as well to clarify the facts," Deutsche Bank said, adding it believed it had already provided all the relevant information related to the "Panama Papers."
The news comes as Deutsche Bank tries to repair its tattered reputation after three years of losses and a drumbeat of financial and regulatory scandals.
Christian Sewing was appointed as chief executive in April to help the bank to rebuild. He trimmed US operations and reshuffled the management board but revenue has continued to slip.
Deutsche Bank shares were down more than 3 percent and have lost almost half their value this year.
The investigation was triggered after investigators reviewed so-called "Offshore-Leaks" and "Panama Papers," the prosecutor said.
The "Panama Papers," which consist of millions of documents from Panamanian law firm Mossack Fonseca, were leaked to the media in April 2016.
Several banks, including Scandinavian lenders Nordea and Handelsbanken have already been fined by regulators for violating money laundering rules as a result of the papers.
The prosecutors said they are looking at whether Deutsche Bank may have assisted clients to set up offshore companies in tax havens so that funds transferred to accounts at Deutsche Bank could skirt anti-money laundering safeguards.
In 2016 alone, over 900 customers were served by a Deutsche Bank subsidiary registered on the British Virgin Islands, generating a volume of more than $353 million, the prosecutors said.
They also said Deutsche Bank employees are alleged to have breached their duties by neglecting to report money laundering suspicions about clients and offshore companies involved in tax evasion schemes.
The investigation is separate from another money laundering scandal surrounding Danish lender Danske Bank, where Deutsche Bank is involved.
Danske is under investigation for suspicious payments of more than $227 billion from 2007 onward and a source with direct knowledge of the case has told Reuters Deutsche Bank helped to process the bulk of the payments.
A Deutsche Bank executive director has said the lender played only a secondary role as a so-called correspondent bank to Danske Bank, limiting what it needed to know about the people behind the transactions.
Weaknesses in Deutsche Bank's controls that aim to prevent money laundering have caught the attention of regulators on both sides of the Atlantic. The bank has publicly said that it agreed it needed to improve its processes to properly identify clients.
In September, Germany's financial watchdog — BaFin — ordered Deutsche Bank to do more to prevent money laundering and "terrorist financing," and appointed KPMG as third party to assess progress.
In August, Reuters reported that Deutsche Bank had uncovered further shortcomings in its ability to fully identify clients and the source of their wealth.
Last year, Deutsche Bank was fined nearly $700 million for allowing money laundering through artificial trades between Moscow, London and New York. An investigation by the US Department of Justice is still ongoing.
Deutsche Bank has been under pressure after annual losses, and it agreed to pay a $7.2 billion settlement with US authorities last year over its sale of toxic mortgage securities in the run-up to the 2008 financial crisis.
By Arno Schuetze and Tom Sims/Reuters
Editing by Jane Merriman and Keith Weir.