The financial watchdog, the FCA, says its work monitoring the new pension freedoms has unearthed 5 scams affecting "multiple consumers".
Better-off pensioners appear to be most vulnerable to being scammed.
The watchdog's director of policy, Chris Woolard, told MPs that ten thousand people had filled in an online form asking for details of scam attempts since the freedoms were launched in April.
160 cases were sent for assessment by enforcement officers, of which 5 were now "ongoing operations".
Mr Woolard said the average scam involved losses of between £18,000 and £20,000 per investor.
"So far we've not seen evidence of a spike in scams overall," he added.
But scammers were turning their attention to pensions, now that the over-55s had the right to cash in their funds as and when they chose.
Criminals who had been concentrating on draining their victims bank accounts might now decide to transform themselves into fake pension providers.
Richer pensioners, who had already dabbled in the stockmarket and were more confident about investments, were in most danger of being duped by fraudsters.