Police have raided offices of German engineering firm Siemens, investigating allegations of embezzlement and corruption. About 30 business premises and private homes were searched as part of the investigation.
German media reported that the probe was triggered by claims that certain Siemens staff had paid bribes to win some contracts. Siemens said it was co-operating with the investigation.
The firm's headquarters in Munich was among the buildings searched.
"Certain Siemens employees have engaged in fraud," the Associated Press news agency reported Andreas Schwab, a Siemens spokesman, as saying. "We are co-operating fully with the investigation."
It is not yet known whether any senior executives were targeted into Wednesday's operation.
More than 200 officers, prosecutors and tax inspectors were involved in the raids.
"There is a suspicion that individual staff have embezzled money," Anton Winkler, a Munich prosecutor, said.