The monthslong investigation into the high-profile graft case involving late business tycoon Sung Woan-jong and President Park Geun-hye’s top aides came to a close Thursday with the prosecution indicting, without detention, two of the eight political heavyweights implicated in the scandal.

The Seoul Central District Prosecutors’ Office filed charges against former Prime Minister Lee Wan-koo and South Gyeongsang Province Gov. Hong Joon-pyo for violating the Political Fund Act by accepting illicit political funds from Sung, the deceased chairman of Keangnam Enterprises, it said in a press briefing Thursday afternoon.

The charges were dropped against six other politicians ― ruling Saenuri Party lawmaker Rep. Hong Moon-jong, Incheon Mayor Yoo Jeong-bok, Busan Mayor Suh Byung-soo and incumbent Presidential Chief of Staff Lee Byung-kee and his two predecessors, Huh Tae-yeol and Kim Ki-choon ― who were also suspected of receiving shady money from Sung, due to lack of evidence and the statute of limitations expirations, the prosecution said.

Both Gov. Hong and ex-premier Lee expressed regret over the prosecution’s decision.

“Lee’s truth is more powerful than anything, and he will strive to clear his charge,” Suh Joon-won, a close aide to the former prime minister, said on behalf of Lee. He also questioned the investigation process, which he claimed had not given Lee a right to defend himself.

Hong said in a press release that he “deeply regretted” the decision to charge him with receiving illicit political funds. He said he had nothing to do with the late businessman, calling the prosecution’s actions “the result of political decision.”

The indictment comes nearly three months after prosecutors launched the investigation into Sung’s claims that he offered illegal campaign money to eight politicians close to President Park.

Sung took his life in April, leaving a hand-written note in his pocket that listed the names of the politicians and the bribe sums he claimed to have handed over, which triggered a public backlash against the Park administration.

The prosecution said that it obtained circumstantial evidence that Sung offered 100 million won ($89,000) to Hong in June 2011, when the four-term lawmaker was running for the leadership of the Grand National Party, the precursor to the ruling Saenuri Party.

Lee is suspected of having received 30 million won from Sung in April 2013 during his bid in the parliamentary by-election. He stepped down as prime minister on April 27 amid the spiraling graft scandal.

In the press briefing, investigators said that they secured evidence that Roh Geon-pyeong, an elder brother of late President Roh Moo-hyun, accepted 500 million won in illegal political money from Sung in 2007 in return for granting him a presidential pardon by exerting influence on government officials. Sung was then sentenced to six months in jail, suspended for a year, on charges of embezzlement.

But it decided not to indict the former president’s brother as the statute of limitations had expired.

As part of the investigation, the prosecution also sent inquiry letters in late May to the six politicians listed in Sung’s memo other than Hong and Lee, requesting information on their affairs with Sung, as well as their roles at the ruling party in the run-up to the 2012 presidential election.

Unsatisfied with the reports, prosecutors called in the ruling Saenuri Party’s three-term lawmaker Rep. Hong for questioning in early June over allegations that he took 200 million won in illegal campaign funds from Sung for then-presidential candidate Park in 2012. But the prosecution allegedly could not obtain any evidence.

The prosecution expanded its investigation into the opposition bloc in late June, calling in Rep. Kim Han-gil, the ex-chairman of the main opposition New Politics Alliance for Democracy party, which the opposition party viewed as “politically motivated” to shield the Park administration. Investigators suspected Kim of accepting illegal funds from Sung, though he was not on Sung’s list.

Prosecutors also accused Saenuri Party Rep. Rhee In-je of having taken bribes worth 20 million won from Sung just before the 2012 general election.

Both Kim and Rhee have been asked to appear for questioning by prosecutors, but they refused, citing their “busy schedule” and “innocence.” The prosecution said that it would continue to investigate the two politicians for bribery.

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)