Special prosecutor Cho Joon-woong, looking into allegations of tax evasion and breach of trust involving Samsung Group Chairman Lee Kun-hee, said he "will announce the findings of the probe Thursday."
Lee has apparently admitted to some lesser infractions, and sources close to the case said allegations of bribery were not substantiated, Yonhap News Agency reported.
Whistle-blower Kim Yong-chul triggered the investigation in January, claiming Korea's largest company set $205 million aside in hidden accounts. He also claimed Lee illegally transferred assets to his son, Jae-young.
The funds, with senior executive names attached to them to cover up Lee's assets, were found and may lead to the tax evasion charges, Yonhap reported.
Lee was summoned to speak with prosecutors twice, on one occasion telling reporters, "case by case. Not 100 percent."
Many interpreted the remark as Lee saying he would resign, but Samsung Group denied that was his intention.