Europol director Rob Wainwright, center, speaks at a news conference in The Hague outlining an international match-fixing scandal in soccer. (ROBIN VAN LONKHUIJSEN/EPA)

Corruption and match-fixing in international soccer are far more organized and widespread than previously known and reach to the very upper echelons of the world’s most popular sport, European police authorities said Monday.

Releasing the findings of an 18-month probe that they said threaten the very integrity of the game, officials from Europol, the European Union’s joint police organization, said a crime syndicate based in Singapore was involved in fixing the results of nearly 700 games in Europe, Africa, Asia and Latin America between 2008 and 2011.

They said the corruption reached the sport’s three biggest competitions, the UEFA Champions League and qualifying games for the European Championship and the World Cup, a quadrennial tournament watched on television by hundreds of millions of people around the world.

“This is the first time we have established substantial evidence that organized crime is now operating in the world of football,” Europol director Rob Wainwright said at a news conference in The Hague.

While gambling and match-fixing linked to Asian betting syndicates and organized crime have vexed soccer for some years, the scope of the corruption outlined in Monday’s report was unprecedented, not just for soccer but for professional team sports.

The Europol report’s description of criminal elements infiltrating players and officials with bribes to determine the outcome of games represents the nightmare scenario for professional sports leagues. While hundreds of millions of dollars are bet on big sporting events such as Sunday’s Super Bowl, U.S. leagues such as the National Football League go to great lengths to guard against exposing themselves to the influence of organized crime.

“When sports move from unscripted, honest athletic competition to scripted entertainment like we see in the movies and on television and Broadway shows. . . that is the scenario in which sports consumers and fans begin to tune out,” said Ryan Rodenberg, an assistant professor of sport management at Florida State University.

Major League Soccer, the U.S. professional soccer league, said it had not been contacted by Europol investigators.

“While we have faith in the integrity of those associated with MLS, we will not ignore what has already transpired around the world. We are not so naive as to think we are immune,” MLS Executive Vice President Nelson Rodriguez said. “We are hiring a director of security who will be charged with developing an integrity program as well as additional defensive measures. This area will be a primary focus.”

Rodriguez said MLS has taken a number of steps aimed at identifying any possible match-fixing. He said these include monitoring gambling activity internationally and in Las Vegas, training and education efforts and a ban on phones and other electronic communication devices in locker rooms beginning an hour before the start of games.

Europol said more than 400 individuals from 15 countries, including players, were involved in the suspicious matches in Europe.

“This is a sad day for European football,” Wainwright said. The scandal is “on a scale and in a way that threatens the very fabric of the game.”

Gamblers collected almost $11 million in profits on the tainted games and spent $2.5 million on bribes to team officials and players, Europol said.

An estimated $3 billion is bet on soccer games daily worldwide.

While soccer match-fixing in Europe has been identified in the past, and has led to a number of prosecutions, officials said the Europol probe exposed a much more pervasive problem. They said they feared the problem could even be much broader.

“We are surprised by the breadth of allegations both in terms of geography and numbers of games,” U.S. Soccer Federation President Sunil Gulati said. “The problem strikes at the very core of sports.”

According to the Reuters news agency, German investigators said games in that country were implicated as were games in Turkey, Switzerland, Belgium, Croatia, Austria, Hungary, Bosnia, Slovenia and Canada. Suspicious games had also been identified in Africa, Asia and Latin America.

U.S. national team players said Monday that they had not heard or read about the investigation before reporting to practice in Miami. The U.S. squad is preparing for a 2014 World Cup qualifier Wednesday in Honduras.

Many of the Americans compete for prominent European clubs and perform on the sport’s largest stages, including England’s Premier League, Italy’s Serie A and Germany’s Bundesliga.

“You see it and hear about it [periodically] — I don’t know how it all works,” said U.S. goalkeeper Tim Howard, who plays for Liverpool-based Everton and has been based in the prestigious English league for almost 10 years. “It seems silly, but people continue to try to do it, I suppose.”

Asked if he had ever been approached, Howard said: “I don’t know what I would do. I think I would laugh at the person. I wouldn’t take it seriously. It all sounds silly to me.”

UEFA, European soccer’s governing body, said it was awaiting further information from Europol, Reuters reported.