In a statement on Tuesday, the public prosecutors in Germany's financial capital said a Frankfurt-based lender had granted Wirecard the credit in 2018 and extended it in 2019 without requiring collateral to protect against losses.
The prosecutors didn't name the bank, but KfW separately said that its subsidiary IPEX-Bank was the subject of the investigation.
"We confirm that the police and the public prosecutor's office have conducted investigations at the premises of KfW IPEX-Bank in connection with our financing of Wirecard," a spokesman said.
($1 = 0.8522 euros)
(Reporting by Patricia Uhlig; Writing by Tom Sims, editing by Emma Thomasson)