According to Reuters, many of those who "sighed with relief" last week could be pursued to pay back their profits and possibly some of their principal.
Jeff Marwil, an attorney who helped the bankrupt Bayou Group of hedge funds recover money from past investors, told the site that the law demands returns if it is judged that investors were aware or should have been aware of problems with a fund.
Investors who exited up to two years before a collapse can be affected, although state statues can extend this to up to six years.
Phillip Bentley of Kramer, Levin, Naftalis & Frankel added that while many investors will have withdrawn for legitimate reasons such as buying a house or funding their child's education, the trustee in charge of liquidating Bernard L Madoff Investment Securities could still pursue them as his job is to "bring in assets any way he can".
"Potentially the numbers are enormous," he warned.