Police said that the most recent losses were on April 18 when members of staff at doctors' surgeries in Liskeard and Newton Abbot had their wallets stolen.
In the days following the thefts, the victims received bogus phone calls which have led to fraudulent activity.
In both cases the caller, claiming to be from their bank, told the victims that arrests had been made and their property had been recovered.
The caller then requested the victims' bank PIN codes to verify their account allowing them to make large withdrawals and purchases using the victims' details.
After initial enquiries, police have identified a series of crimes with similar circumstances at businesses such as hotels, a golf club and a hospital in areas including Liskeard, Tiverton, Exeter, St Austell, Ottery St Mary and Chulmleigh.
PC Phil Tucker, of Devon and Cornwall Police, explained: 'We believe this to be a professional outfit operating across the force area and not likely to be anyone known to the victims. We would emphasise that people should challenge unknown people even if they appear to be staff.
'We are advising people to be vigilant when dealing with unsolicited calls.'
Banks and building societies will never ask for PIN numbers or sensitive information to be disclosed over the phone. If in any doubt, take the contact details and phone the police.
The website, http://www.actionfraud.org">www.actionfraud.org, offers information and advice about the common and current frauds/scams that occur. It also offers advice on how to deal with them.
Anyone who has any information is asked to call the police as soon as possible.