Four employees of Swiss bank Credit Suisse have come to the attention of public prosecutors in Germany.
Along with a former bank employee, the four workers are suspected of aiding clients with tax evasion, the Düsseldorf public prosecutor told the Reuters news agency on Thursday.
As part of the investigation, raids were carried out in the Lake Constance region this week. Anonymous documents sent in July helped tip off the prosecutor.
It appears that false identities were used in connection with life insurance policies.
Previously, the authorities were investigating the deeds of unknown suspects, but now there is information linking them to the five bank professionals.
A Credit Suisse spokesman said the bank was aware of the investigation.
swissinfo.ch and agencies