Police investigating last week's kidnapping and murder of a woman are expanding their probe considering the possibility of a mastermind behind the crime, officials said Tuesday.

Three suspects were formally arrested Monday for allegedly abducting a 48-year-old woman in Seoul's posh Gangnam district and killing her.

According to the Suseo Police Station in southern Seoul, investigators have found tens of millions of won were transferred from a cryptocurrency company official to one of the suspects, surnamed Lee, before the incident occurred.

The police are investigating whether the payment is linked to the crime and have barred several people who had financial dealings with Lee or invested with him jointly in cryptocurrencies from leaving the country.

The three people were detained Friday on suspicions of kidnapping the woman near an apartment building in Gangnam Ward on Wednesday night, killing her the following day and burying her body on a hill in Daejeon, about 140 kilometers south of the capital.

Investigators initially suspected that Lee masterminded the crime.

The other two accomplices, surnamed Hwang and Yeon, told the police that Lee proposed kidnapping the victim to steal her money and that they planned the crime for two to three months.

Lee denied the charge. But the police confirmed he gave 7 million won ($5,363) to Hwang after proposing the crime.

Lee told the police that he suffered a loss of 80 million won from his investment in a cryptocurrency company where the victim had worked and that he also once worked for the firm.

The police also booked another 20-something man Sunday for investigation over suspected involvement in the murder.

Upon a proposal from Hwang, he had allegedly tailed her before quitting in mid-March. Police were reviewing whether to file for a warrant to arrest him as well. (Yonhap)