The sum is part of the total KRW14.56bn ($13.38m) that went missing from a casino building belonging to Landing International Development Ltd.

According to the Yonhap News Agency, the investigation began on 4 January.

The cash was in the care of a 55-year-old Malaysian female executive who went on vacation at the end of last year and remained out of contact ever since.

The operator reported the executive had taken the cash out of the Jeju casino's safe complying with all due security procedures.

KRW8.15m was recovered from the Jeju casino's VIP room safe and about KRW4bn was found in a place where the employee used to stay.

The search for her is still ongoing, but the police now have two more suspected co-perpetrators who had no links with Landing.

The woman and one of the accomplices (a Chinese national of 30-something years) are said to be overseas, while the third suspect is predicted to still be in South Korea. The genders of the accomplices remain unknown.

Police said: "All the retrieved money is cash in new 50,000-won bills. The possibility of other accomplices being involved in the theft cannot be ruled out."