Prosecutors on Wednesday continued their questionings into a corruption-laden urban development scandal engulfing South Korean politics, summoning the four key suspects of the high profile case again all on the same day for possible cross-examinations.

Prosecutors are looking into suspicions over how a previously unheard-of asset management firm, Hwacheon Daeyu, and its seven affiliates reaped astronomical profits from a 2015 project to develop the Daejang-dong district in Seongnam, south of Seoul, into an apartment complex.

Kim Man-bae, Nam Wook and Jeong Young-hak -- private partners of the project -- are alleged to have colluded with Yoo Dong-gyu, former acting president of Seongnam Development Corp., to have the asset firm take part in the lucrative project.

The scandal has received intense media coverage amid questions about its potential impact on next year's presidential election, as Yoo is widely regarded as an associate of Gyeonggi Province Gov. Lee Jae-myung, who is now the ruling Democratic Party's presidential nominee.

The main opposition People Power Party has claimed Lee, who was serving as Seongnam mayor when the project was launched, was behind the whole scheme.

According to sources, investigators at the Seoul Central District Court summoned Kim, Nam, Jeong and Yoo for questioning all on Wednesday.

Yoo is suspected of receiving 800 million won (US$681,657) in bribes in exchange for designing the profit distribution arrangements in a way to benefit Hwacheon Daeyu while inflicting losses on the city. The three others are alleged to have discussed raising 35 billion won in order to pay seven influential people 5 billion won each in bribes.

Investigators are reportedly following leads largely based on secretly taped conversations between the project's key players recorded by Jeong, an accountant who owns Cheonhwa Dongin No. 5, an affiliate of Hwacheon Daeyu.

However, they reportedly have yet to find a clear breakthrough in the case, as the suspects are reportedly disputing each other's claims and shifting blame to one another.

The court also rejected an arrest warrant request for Kim, the owner of Hwacheon Daeyu, last week, saying the prosecution failed to present sufficient grounds for his arrest. The prosecution also did not seek an arrest warrant for Nam, who returned to South Korea from Los Angeles on Monday for questioning, even after having questioned him for two straight days.

Amid the apparent stalemate in the investigation, it is widely expected prosecutors may conduct cross-examinations between the suspects to verify conflicting statements and the contents of Jeong's recordings. (Yonhap)