Less than a month out from the 2015 Rugby World Cup, London police are investigating the production and sale of counterfeit tickets.
Fans are being urged to only buy tickets from official outlets to guarantee access to tournament matches after it was discovered fake tickets were in circulation.
Any tickets bought from unofficial sources can be cancelled without a refund under Rugby World Cup's ticket terms and conditions.
London Police are working with tournament organisers, England Rugby 2015, and tournament owners, Rugby World Cup Limited, to carry out a full investigation to help ensure that fans are made aware.
World Rugby Chairman, Bernard Lapasset, said: "Fan experience is very much at the heart of what promises to be a very special celebration of Rugby and we urge all fans who are yet to purchase tickets to do so from official channels only or risk being let down.