Democratic Party of Korea Chairman Lee Jae-myung speaks during his meeting with members of the Korea Senior Citizens Association at the National Assembly in Seoul, Nov. 23. Yonhap

Prosecutors have begun tracking the bank accounts of opposition leader Lee Jae-myung and his relatives, informed judicial officials said Thursday, suggesting a forced investigation against the Democratic Party of Korea (DPK) chair is imminent.

The Seoul Central District Prosecutors Office has recently secured a court's warrant to trace the accounts of Lee and his family, apparently to look into anything suspicious about the money transactions between the DPK chief and the people around him, according to the officials.

Prosecutors appear to be checking whether parts of the money received by two of his closest aides, Jeong Jin-sang and Kim Yong, from real estate developers at the center of a corruption scandal in Seongnam, south of Seoul, flowed to Lee's side, they added.

Jeong, a vice chief of staff to the DPK chair, and Kim, who resigned this week as deputy head of the DPK's Institute for Democracy think tank, have been arrested on charges of receiving about 140 million won ($104,000) and 847 million won, respectively, from the Seongnam property developers allegedly given business favors when Lee was the city's mayor.