Deutsche Bank was sued in Florida by a Jewish charitable trust that claims the firm wrongly withheld as much as $3 billion from the heirs to a wealthy German family. The lawsuit claims the bank refuses to return the funds initially deposited by the Wertheim family in accounts opened at what is now Credit Suisse before the rise of the Nazis in Germany. Those accounts were later transferred to Deutsche Bank.

The complaint further charges that Deutsche Bank has “refused to cooperate with the heirs of the Wertheim family fortune in the recovery and return of the monies that they are withholding from the rightful heirs,” and preventing the use of the funds for charitable and other purposes.

Deutsche Bank is “taking the matter very seriously,” said a DB spokesperson, who added: “The accusations are completely unfounded, and Deutsche Bank denies them. All proceedings initiated against Deutsche Bank in this matter have been decided in favor of Deutsche Bank.”

A bulk of the family’s funds were deposited into an account at Credit Suisse in 1931. The Swiss bank protected the family assets through the rise of the Nazis in the 1930s and during World War II, using secret numbered accounts, pseudonyms and trust accounts, according to the complaint. Through a complex series of events, the assets were transferred in 1993 to Deutsche Bank, which misled the Wertheim heirs for many years about the accounts, according to the complaint.