South Korea's prosecution began questioning a former presidential official who initially reported on tips regarding alleged improprieties surrounding former Ulsan City Mayor Kim Gi-hyeon.
The Seoul Central District Prosecutors' Office on Thursday summoned the official, surnamed Moon, to learn of the process through which he received and handled the tips from current Ulsan Deputy Mayor Song Byeong-gi in 2017.
Prosecutors are expected to grill Moon on whether he requested the information from Song and if anyone at the presidential office or National Police Agency intervened in the process.
The investigative agency reportedly has evidence that a police investigation into Kim ahead of last year's Ulsan mayoral election may have been unduly influenced by the top office.
Kim lost the election to current Ulsan Mayor Song Cheol-ho, a close confidant of President Moon Jae-in.
On Wednesday, the presidential office dismissed allegations that it conducted illegal surveillance before instructing police to investigate suspected corruption surrounding the former Ulsan mayor.