Prosecutors on Wednesday raided five locations of Samsung Electronics Co.'s after-services unit as part of an ongoing probe into the conglomerate's suspected attempts to sabotage labor union activities.

Investigators from the Seoul Central District Prosecutors' Office searched a warehouse in the Suwon headquarters of Samsung Electronics Service and its four regional offices in Busan to confiscate evidence, including documents and digital files, the office said.

Wednesday's raid comes after the prosecution carried out a search warrant at two other regional offices just outside of Seoul and officials' residences last week.

Prosecutors have been investigating allegations that Samsung ran an organized scheme aimed at hampering the establishment and operations of labor unions.

Documents obtained by the prosecution indicate that Samsung allegedly had a "master plan" containing details of action plans and guidelines on how to disrupt labor union activities.

The labor union officials who were questioned the previous day also claimed there were serious abuses by the company and led to a suicide by one worker in 2013. (Yonhap)