Police arrested a fourth man on Wednesday as part of an investigation into allegations of spying during a fiercely contested bid process to select who will move into London's Olympic stadium after the 2012 Games.
A 45-year-old man was detained in south London by officers from the Economic and Specialist Crime Command on suspicion of fraud. Material was seized during a search of a house, Scotland Yard said in a statement.
It is the fourth arrest since November following allegations by soccer club West Ham United and the public body the Olympic Park Legacy Company (OPLC) in respect of the unlawful obtaining of information.
OPLC chairwoman Margaret Ford has accused Premier League soccer club Tottenham Hotspur of putting all her 14 board members under surveillance.
The arrests are the latest twist in a bitter dispute over who should move into the 438 million pound main stadium on the Olympic Park in east London once the athletes have gone home.
Tottenham went to court seeking a judicial review after the OPLC awarded West Ham preferred bidder status last February.
It argued a 40 million pound loan from bid partner Newham Council gave West Ham an unfair economic advantage and made the decision unlawful. An anonymous party also threatened to challenge the decision at the European Court.
But Tottenham dropped its legal action when the government pulled the plug on the deal in October and decided to keep the stadium in public ownership instead.
On November 8, a 29-year-old man was arrested in Sussex, southern England, while later that month a 39-year-old man was detained in Surrey.
A third man, 57, was held on January 11 in Cheshire, northwest England.
All were arrested on suspicion of fraud and bailed pending further inquiries, and a number of residential and business properties have been searched.
Ford told the London Assembly late last year: My board were put under surveillance by Tottenham Hotspur and the chairman of Tottenham Hotspur felt confident enough to say that in the Sunday Times several months ago, that all 14 members of my board were put under surveillance.
The Metropolitan Police are now conducting an investigation into that surveillance. There has been all kinds of behaviour here that I could not have anticipated which, believe me, has not been pleasant in the last 12 months.
Tottenham have strongly denied any suggestion they had carried out surveillance on executives at West Ham or the OPLC.
We consider the making of this baseless accusation to be wholly inappropriate and irresponsible, a club statement said at the time.
We totally reject this accusation in the strongest possible terms.
(Reporting by Avril Ormsby, editing by Justin Palmer)