A match-fixing ring with more than 200 suspected members fixed or tried to fix around 200 matches across Europe, including three in the Champions League, in what UEFA called the biggest betting scandal in Europe.
Bochum state prosecutor Andreas Bachmann said at a news conference on Friday initial estimates put the illegal gains at about 10 million euros ($14.85 million) but he added that the figure was just "the tip of the iceberg".
Police in Germany, Britain, Austria and Switzerland cracked down on the ring on Thursday, staging simultaneous raids that resulted in 15 arrests in Germany and two in Switzerland.
Officers also seized one million euros ($1.49 million) in cash or goods as part of the investigation into the suspected manipulation of games across nine European leagues.
Some 50 properties were searched in the four countries.
"We at (European soccer's governing body) UEFA are stunned by the magnitude of this," UEFA representative Peter Limacher told reporters at a Bochum police news conference on Friday.
"This is undoubtedly the biggest match-fixing scandal that European football has ever seen. Now we must do everything to make sure those referees, players and officials are taken to justice."
HUNDREDS OF MATCHES
Bochum police said 200 people were suspected of involvement in attempts to rig about 200 matches in 2009, some during the current season.
No details of which teams or players and officials involved were released.
"There was a group of individuals who did or tried to influence matches with money and make illegal profit through the placing of bets," said Bachmann.
A City of London spokeswoman said in a statement: "Following a request from German law enforcement officers, City of London police assisted in the execution of a search warrant in the Greater London area on Thursday."
She added no arrests had been made and just one property was searched.
Some 32 matches in Germany's lower divisions as well as dozens of first or second division matches in Turkey, Belgium, Bosnia, Hungary, Croatia, Switzerland, Austria and Slovenia were under investigation.
Twelve matches in the Europa League, the second-tier European club competition behind the elite Champions League, were also under suspicion as well as several Under 21 European Championship qualifiers.
In 2005, Germany was rocked by a betting scandal involving Bundesliga referee Robert Hoyzer, who rigged matches as part of an international illegal betting gang and was sentenced to two years and five months in prison.
"Even if the German professional football is only partly involved we will fully support the effort to expose this," German League chief Reinhard Rauball said on Friday.
"We owe it to the fans to do everything within our power to offer a clean competition."