The Securities and Exchange Commission (SEC) is searching for a mystery player that it believes orchestrated a lucrative insider trading scam before News Corporation’s $5 billion (£2.5 billion) bid for Dow Jones last month.

The American watchdog is suing a husband and wife in Hong Kong for allegedly making an $8 million profit trading on inside information, but it is thought to view them as intermediaries working for a mystery architect.

The SEC won a temporary court order freezing $23 million of cash held in the bank accounts of Kan King Wong and his wife, Charlotte Ka On Wong Leung, both of whom work in the telecoms industry.

It aims to trace the trail of money back through the “chain of custody, looking for intersections” as it seeks to determine who orchestrated the insider trading, according to one source.

The SEC, which declined to comment, is also investigating other potential cases of insider trading, such as a surge in options trading the day before the approach was announced, along with the possibility that they are also connected to the same “mystery mastermind”.

If the SEC investigation of alleged insider trading in Dow Jones stocks turns its focus towards the links between Sir David Li and Michael Leung, Hong Kong could be rocked by a potential scandal of epic proportions. Sir David is a Dow Jones director with close ties to Mr Leung, who is Charlotte Ka On Wong Leung’s father and who the SEC alleges provided $3.1 million of the cash his daughter invested.

Between them, the two old friends represent the two sides of Hong Kong wealth. More than £45 million of Mr Leung’s fortune was made when he sold China Resources People’s Telephone, the mobile phone venture that he founded, to China Mobile in 2005. Later he launched a line of expensive lingerie with two of his children.

Sir David’s early business ventures included selling secondhand bicycles as a student in Cambridge, but he has since been a career banker and he represents the powerful “old money” that still holds so much sway.

The links between the two may hold the key to the biggest question still unanswered by the SEC investigators: did Mr Leung’s daughter and her husband know that Dow Jones would receive a $5 billion bid from News Corp two weeks before it was announced, and, if so, how?

News Corp did not submit its formal offer letter to the Dow Jones board until April 15, whereas the couple began to buy shares on April 13.

Sir David told The Wall Street Journal, which is owned by Dow Jones, that he believed that he did not find out about the offer until a board meeting on April 17. He also said: “I did not disclose to anyone, not even my wife, any information about Dow Jones.”

Sir David’s position on the board of Dow Jones now presents SEC investigators with a possible line of inquiry. However, the SEC is thought to be more concerned with following the money trail and seeing where it leads than starting with an individual and seeking to determine their involvement.

It is not illegal to possess inside information, but it is a crime to conduct share trades based on such knowledge.

The upper echelons of the Hong Kong business elite are famed for their cosiness, but even by those standards the ties between Mr Leung and Sir David are tightly wound. The two men both hold honorary fellowships from Hong Kong’s Lingnan University and Mr Leung is an active member of the Friends of Cambridge University Hong Kong chapter, which was founded 25 years ago by Sir David.

The clearest business link is that Mr Leung is a director of the Canadian subsidiary of the Bank of East Asia. Sir David is the chairman and chief executive of the financial powerhouse, which acted as the principal banker to Mr Leung’s telecoms empire.

Mr Leung said yesterday: “I will not comment for now because the case is being handled by lawyers.”

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