Police conducted their first questioning of the inmate the previous day after the state forensic agency found that DNA collected from a victim's underwear matched his.

But the man denied involvement in the Hwaseong murder cases during the two consecutive interrogations, police officials said.

The Gyeonggi police agency plans to hold its third interrogation of the suspect Friday.

As the suspect has consistently denied any role in the Hwaseong murders despite three sets of DNA evidence, the police investigation is expected to drag on longer than originally expected, watchers say. Without a confession from the suspect, it will be difficult for police to confirm him as the real perpetrator and conclude their probe, they say.

Police said they will mobilize all possible methods and efforts to find any clues about the suspect's link to other unsolved murder cases in Hwaseong.

"It is difficult to disclose details of the probe but police will step up questioning of the suspect as his confession will be the most important thing," a police official said.

The suspect is currently serving a life sentence for the murder and rape of his sister-in-law at his home in Cheongju, North Chungcheong Province, in 1994. He was reportedly born in Hwaseong and lived there until 1993, when he moved to Cheongju.

The suspect remained at large for nearly 30 years despite police efforts to track down the criminal. More than 2 million police officers, a record number for a single case, were mobilized.

Because the statute of limitations regarding the Hwaseong case expired in 2006, the suspect will not be punished even if the charges are confirmed. (Yonhap)