Six people arrested in connection with the collapsed Cornish-based foreign exchange company Crown Currency Exchange have been released on bail.
The three men and three women were arrested on suspicion of money laundering and fraud offences on Tuesday.
The arrests took place at addresses in Cornwall and Hertfordshire.
The exchange firm, based in Hayle in Cornwall, collapsed in October owing customers more than £16m.
The six were released on bail until July.
Devon and Cornwall Police said they had now linked the collapse of another financial company to their criminal investigation.
Det Insp Paul Bean, head of the force's Economic Crime Unit, said: "This is a lengthy and complicated investigation in which there are many lines of inquiry to pursue.
"It is anticipated that there are over 8,000 victims of crime in relation to the collapse of these companies."
Crown Currency Exchange, which was established six years ago, allowed individuals and business customers to pre-order foreign exchange at a set price up to a year in advance.
It provided money in 80 different currencies, as well as travellers' cheques and money transfers.