Four men have been arrested by police in Hertfordshire on suspicion of taking part in a fine wine fraud.
As many as 70 victims are believed to have been tricked into parting with thousands of pounds for wines that do not exist.
The wine was offered for sale "en primeur" - still in the barrel.
Hertfordshire police want to speak to anyone approached to invest in firms called International Wine Commodities or Bordeaux Wine Trading Company Ltd.
Police said customers were told the wine was being held in bonded warehouses in the UK and would be worth £5,000 a case as a long term investment.
A spokesperson for Hertfordshire Police said officers want to speak to anyone across the UK who may have been approached to buy cases of wines from these companies over the past two years.
The four men who were arrested were later released on bail.
They said the company was not to be confused with the Bordeaux Wine Company Ltd of Cavendish Place, London W1.