The Corruption Investigation Office for High-ranking Officials(CIO) has summoned prosecutor Son Jun-sung, a key figure in an investigation into alleged political meddling, for a second time.

Son appeared for questioning Wednesday morning as a suspect, just eight days after being interrogated for the first time.

When he was head of investigative information policy at the Supreme Prosecutors' Office(SPO) last April, Son allegedly ordered officials to file complaints about pro-government figures and to collect data before the general election.

He then allegedly delivered this to Rep. Kim Woong of the main opposition People Power Party(PPP). Son has reportedly denied the allegations.

The CIO is expected to continue grilling Son based on the outcome of Kim’s interrogation and a raid of the SPO's inspection unit last week.

The CIO may also question Son about a separate probe into PPP presidential candidate Yoon Seok-youl for allegedly ordering the documentation of traits of judges on politically sensitive cases while he was chief prosecutor.