Federal investigators are still trying to figure out what happened to the operator of a massive hedge fund — and possibly millions of dollars managed by the missing man.

Arthur G. Nadel, 75, was reported missing by family members Wednesday. Police said he seemed "very distraught" in a note left for his family. His car was found Thursday in an airport parking lot.

It remains unclear exactly how much money had been invested or how much was missing, though one investor has said the fund was worth as much as $350 million.

Sarasota Police have received at least seven complaints from investors. Some say they lost more than $700,000.

Local authorities are working with the FBI and the Securities and Exchange Commission to find Nadel.