The blue-chip company filed for insolvency last month, owing creditors almost $4 billion after disclosing a 1.9 billion euro ($2.17 billion) hole in its accounts that auditor EY said was the result of a sophisticated global fraud.
Alix Partners has been tasked with finding out which Wirecard employees, including executive and supervisory board members, knew what about potentially criminal incidents, the people said.
Findings are expected to be valuable in any litigation against Wirecard managers and claims to their directors and officers liability (D&O) insurers.
The probe is being carried out with the consent of the insolvency administrator for Wirecard, they added.
Alix Partners declined to comment, while Wirecard and the administrator were not immediately available for comment.