More evidence has been found to support alleged upper-level involvement in the Seongnam land development project as prosecutors continue to investigate.

Through questioning key witnesses, prosecutors have confirmed the deletion of a phrase on restitution of surplus development gains from project documents, which is suspected to have been ordered by a senior official.

Private investors reaped excessive profit from the project thanks to the removal of the phrase. 

After arresting former acting president of Seongnam Development Corporation, Yoo Dong-kyu, on Sunday, the prosecution questioned a series of key witnesses who worked with Yoo at the firm. Some testified to the removal of the phrase.

Allegations have been raised within both political parties over the scandal, which took place in 2015 when leading Democratic Party presidential contender Lee Jae-myung was mayor of Seongnam.