The City watchdog has probed 250,000 transactions on the hunt for money owed to individuals following the collapse of foreign exchange company Premier FX.
The Financial Conduct Authority (FCA) chief executive Andrew Bailey said his investigators would not stop until they had traced the missing cash.
The foreign exchange firm, based in Portugal with offices in London, encouraged customers to leave cash with the company to benefit from exchange rates, before buying a holiday home.
Dozens of victims are believed to have lost up to €400,000 (£347,000) after the company’s collapse last year.
Premier FX was regulated by the FCA for money transfers but was not authorised to accept deposits and hold funds.
Bailey told the Treasury Select Committee investigators had trawled through 250,000 transactions and vowed to keep going until the money was recovered.
He said: “My team has so far looked at a quarter of a million transaction records to try to trace the money, and we will not stop doing that.”
The company’s chief executive and founder Peter Rexstrew died in June after undergoing heart surgery, according to local media in Portugal.
Premier FX was then put into administration by the FCA in August, and Menzies LLP were appointed joint liquidators last month.
Bailey said: “The person involved in this activity is said to be dead.
“It’s incumbent on his relatives and business partners to tell us where the money is.”
He added that his first priority was to find the money for the victims but the FCA could look inwardly if it “missed the clues”.