London 2012: Advice to watch out for Olympic pickpocket gangs
18 July 2012 Last updated at 12:55 BST
Scotland Yard says it has received intelligence that organised gangs from South America and Eastern Europe are planning a crime blitz during the Olympic Games.
Some gangs are already in the UK, fuelling a surge in petty crime.
A number of police operations have been launched to tackle these gangs, raiding their homes and targeting suspects on the streets.
Chris Rogers travelled to Barcelona, a hotspot for "career pickpockets", where he found a Romanian gang who claim they are planning to target Olympic tourists.