Sambu Construction's logo is seen on the exterior wall of the firm's former headquarters in Jung District, Seoul, Feb. 26. Yonhap

The Financial Supervisory Service (FSS) is intensifying efforts to track the flow of funds in connection with allegations of stock price manipulation involving Sambu Construction, which gained attention as a Ukraine reconstruction-themed stock, officials said Monday.

The main opposition Democratic Party of Korea (DPK) argues that the period of the firm's stock surge coincided with President Yoon Suk Yeol and first lady Kim Keon Hee's July 2023 visit to Ukraine, where the couple discussed reconstruction projects with Ukraine President Volodymyr Zelenskyy and his wife.

The party alleges that this was a case of premeditated stock price manipulation and is calling for a thorough investigation.

The financial watchdog found that former Sambu Construction Chairman Cho Sung-ok, his family and other major shareholders unloaded company shares worth hundreds of billions of won since May 2023 via about 10 accounts.

The profits reaped by these major shareholders from selling shares during the stock price surge are estimated to be at least 10 billion won ($6.9 million).

"We are currently investigating around 200 accounts to track the flow of these profits," an FSS official said.

The FSS is particularly looking into whether these trading profits flowed to Lee Jong-ho, the former head of Blackpearl Invest. Lee is a key figure in the alleged Deutsche Motors stock price manipulation case, in which the first lady was also implicated.

If the former Blackpearl Invest head is found to be involved in the Sambu Construction case, authorities believe he likely shared a portion of the trading profits.

Rep. Lee Jae-myung, leader of the main opposition Democratic Party of Korea, holds up a stock chart of Sambu Construction during a meeting of the stock market activation task force at the Korea Exchange building in Seoul, Nov. 28, 2024. Yonhap

The opposition party pointed out that after the former head of Blackpearl Invest posted a message saying "Check Sambu tomorrow" in a group chat, the trading volume and stock price of the company surged, raising suspicions of stock price manipulation.

Earlier, the construction company's stock price, which had been in the 1,000-won range, skyrocketed to 5,500 won in July 2023 after the firm attended a global forum in Poland in May of the same year to discuss Ukraine's reconstruction projects. Following this participation, the firm was classified as a Ukraine reconstruction-themed stock.

The DPK noted that this period coincided with Yoon's visit to Ukraine with his wife.

The Korea Exchange (KRX) initiated an unusual trading investigation in connection with the case in July last year.

The FSS explained that it immediately launched its own investigation after receiving the results of the KRX's probe in September, forming a team of four investigators.

"Normally, we investigate dozens of accounts in a case, but for this incident, we need to investigate over 200 accounts, so it has taken more time than usual," the FSS official said, clarifying that the delay was not intentional.

This explanation came as the opposition party raised suspicions that the watchdog may be stalling to avoid political fallout, given that no conclusions have been reached yet, despite the investigation having been underway for more than six months.

The official added that the FSS plans to conclude the investigation soon after conducting additional supplementary inquiries.

Rep. Kang Jun-hyeon, center, of the main opposition Democratic Party of Korea, together with other lawmakers including Rep. Min Byoung-dug, right, speaks to reporters during a visit to the Financial Supervisory Service in Seoul, Monday. Newsis

The opposition party, for its part, visited the FSS, also on Monday, urging the watchdog to immediately release the investigation results and refer the case to the prosecution so that the truth can be revealed.

"The Sambu case is a matter related to the Yoon government's foreign and defense policy," Rep. Min Byoung-dug said. "It is an incident where Yoon and his wife met with Ukraine's first lady, the finance minister signed an agreement on financial aid and the land minister invited Sambu Construction, which had not been invited, to participate in the global forum for Ukraine's reconstruction."