ZURICH (AP) ― Soccer is falling under a cloud of suspicion as never before, sullied by a multibillion-dollar web of match-fixing that is corrupting increasingly larger parts of the world’s most popular sport.

Internet betting, emboldened criminal gangs and even the economic downturn have created conditions that make soccer a lucrative target.

Known as “the beautiful game” for its grace, athleticism and traditions of fair play, soccer is under threat of becoming a dirty game.

“Football is in a disastrous state,” said Chris Eaton, director of sport integrity at the International Centre for Sport Security. “Fixing of matches for criminal gambling fraud purposes is absolutely endemic worldwide ... arrogantly happening daily.”

At least 50 nations in 2012 had match-fixing investigations ― almost a quarter of the 209 members of FIFA, soccer’s governing body ― involving hundreds of people.

Europol, the European Union’s police body, announced last week that it had found 680 “suspicious” games worldwide since 2008, including 380 in Europe.

Experts interviewed by the Associated Press believe that figure may be low. Sportradar, a company in London that monitors global sports betting, estimates that about 300 soccer games a year in Europe alone could be rigged.

“We do not detect it better,” Eaton said in an interview with the AP. “There’s just more to detect.”

Globalization has propelled the fortunes of popular soccer teams like Manchester United and showered millions in TV revenue on clubs that get into tournaments like Europe’s Champions League.

Criminals have realized that it can be vastly easier to shift gambling profits across borders than it is to move contraband.

“These are real criminals ― Italian mafia, Chinese gangs, Russian mafia,” said Sylvia Schenk, a sports expert with corruption watchdog Transparency International.

Ralf Mutschke, FIFA’s security chief, admits that soccer officials had underestimated the scope of match-fixing. He told the AP that “realistically, there is no way” FIFA can tackle organized crime by itself, saying it needs more help from national law enforcement agencies.

The growing threat has prompted the European Union’s 27 nations to unite against match-fixing.

“The scale is such that no country can deal with the problem on its own,” said EU Sport Commissioner Androulla Vassiliou.

Gambling on sports generates hundreds of billions of dollars a year, and up to 90 percent of that is bet on soccer, Interpol chief Ronald Noble told the AP in an interview. Eaton, the former FIFA expert, has cited an estimated $500 billion a year.

The total amount of money generated by sports betting would equal the gross domestic product of Switzerland, ranked 19th in the world.

Match-fixing ― where the outcome of a game is determined in advance ― is used by gambling rings to make money off bets they know they will win. Matches also are rigged to propel a team into a higher-ranking division where it can earn more revenue.

FIFA has estimated that organized crime takes in as much as $15 billion a year by fixing matches. In Italy alone, a recent rigging scandal is estimated to have produced $2.6 billion for the Camorra and the Mafia crime syndicates, Eaton said.

Soccer officials are well aware that repeated match-fixing will undermine the integrity of their sport, driving away sponsors and reducing the billion-dollar value of lucrative TV contracts.

FIFA earned $2.4 billion in broadcast sales linked to the 2010 World Cup in South Africa and already has agreed to $2.3 billion in deals tied to the 2018 World Cup in Russia.

The U.K.’s Premier League earned $2.8 billion in broadcast rights for Britain alone in its last multiyear contract. Membership in Europe’s Champions League is worth nearly $60 million a year to each team, according to a lawsuit filed by the Turkish club Fenerbahce.

FIFA president Sepp Blatter has proclaimed “zero tolerance” for match-fixing, and FIFA has pledged $27 million to Interpol to fight it.

Computer experts working for FIFA and UEFA ― the European soccer body ― monitor more than 31,000 European games and thousands of international matches every year, trying to sniff out the betting spikes that can reveal corruption.

So far, however, sports authorities are “proving to be particularly helpless in the face of the transnational resources” available to organized crime, according to a 2012 study on match-fixing.

The report warned that the risk of soccer “falling into decay in the face of repeated scandals is genuine and must not be underestimated.”

Some top soccer officials shy away from the dire warnings of academics and law enforcement officials. UEFA chief Gianni Infantino said in a statement that, on average, 203 games ― 0.7 percent of the matches that UEFA monitors a year ― show some signs of irregularities, “which does not mean they are fixed.”

“It is a small problem, but it’s like a cancer,” Infantino said. “We don’t say 0.7 is nothing. We say 0.7 is 0.7 too much. We can say generally that UEFA competitions are very healthy in this respect.”