Police have reopened an investigation into an alleged fraud case involving a former chairman of the operator of South Korea's largest cryptocurrency exchange Bithumb, informed officials said Monday.

The Seoul Metropolitan Police Agency has been probing Lee Jung-hoon, former chairman of crypto exchange operator Bithumb Korea, after a group of 14 investors filed their second fraud complaint in mid-July, they said.

Kim Byung-gun, chairman of BK Group, an entity specialized in medical and investment businesses, is also under investigation on alleged fraud charges linked to Lee, they said.

In the complaint, the investors said they had offered 718 bitcoins and 7,793 Ethereum, worth 6.92 billion won ($6.01 million), to Kim in October 2018 after he vowed to take over Bithumb Korea and said an unlisted coin called BXA would get issued and listed.

Contrary to Kim's promise to investors and media, however, the takeover of Bithumb Korea never materialized and all of their investments were paid to Lee, they investors argued, saying they believe Kim and Lee are accomplices.

Indeed, the sale of Bithumb Korea fell through in September 2019. Kim reportedly made a downpayment of $100 million to Lee but did not pay the balance. The BXA coins were not listed, leading to huge losses to investors.

A year ago, police conducted a similar investigation into the alleged Bithumb fraud case after a group of investors filed their first complaint.

Then, Seoul prosecutors last month indicted Lee without detention on charges of defrauding Kim out of $100 million. But prosecutors dismissed investors' claims that Lee and Kim had conspired in the allegedly fraudulent sales of BXA coins.

In response, the 14 investors reportedly submitted additional evidence, including recordings, to police vowing to prove collusion between Lee and Kim. (Yonhap)