Prosecutors have reopened the probe into the allegations after they discovered documents during raids of two Samsung Electronics buildings early this year as part of an investigation into bribery suspicions involving former President Lee Myung-bak.

The documents are known to contain details regarding Samsung Group's attempts to hamper workers' efforts to set up labor unions. Samsung is notorious for its "no union" policy.

"We hail the prosecution decision to reopen the case," Ra told reporters as he appeared at the prosecution office. "We will tell the truth for every single page of the 6,000-page document and make sure the damage is proved."

The documents apparently show Samsung continued its sabotage attempts on labor union movements until recently.

They also allege that Samsung had a "masterplan" containing details of action plans and guidelines on how to disrupt labor union activities.

Prosecutors said earlier they plan to check with the union officials if any part of the masterplan had actually been carried out.

Suspicions over Samsung's sabotage were first raised in 2013 by an opposition lawmaker in the disclosure of what she claimed to be Samsung's guidelines against forming of labor unions.

Samsung workers and civic activists filed a complaint against Chairman Lee Kun-hee and other group officials. But the prosecution dropped most of the charges and closed the case in 2015. (Yonhap)