A fourth suspect has been arrested by detectives who are investigating allegations that Tottenham Hotspur spied on Olympic officials during its stadium bid.
Scotland Yard confirmed a 45-year-old man was being held at a south London police station after his property was searched.
The investigation surrounds allegations by West Ham United and the Olympic Park Legacy Company "in respect of the unlawful obtaining of information", the force said.
Sources said an "amount of material was seized" during the search.
Three other men, aged 29, 39 and 57, have been arrested in recent months during the inquiry by the Metropolitan Police's Economic and Specialist Crime Command.
Olympic Park Legacy Company (OPLC) chairwoman Baroness Ford claimed in November that the north London football club had all 14 members of her board monitored by private investigators.
Spurs deny putting officials under surveillance.
A deal with West Ham and Newham Council to use the stadium in Stratford, east London, after the 2012 Games collapsed in October last year, with the Government announcing that the stadium would remain in public ownership.
Tottenham had already lost out to West Ham in the race to become the OPLC's first choice to move into the stadium after the Olympics.
Challenges by Tottenham Hotspur and Leyton Orient, plus an anonymous complaint to the European Commission, had led to fears that court action could drag on for years while the stadium remained empty.
A new tender process is being launched by the OPLC and the showpiece venue, complete with an athletics track, will now remain in public ownership and be rented out to an anchor tenant.