Uefa has revealed that none of the 15 matches under suspicion of match-fixing were Euro 2008 qualifiers.
European football's governing body has given a 96-page report to Interpol alleging that 15 games in a variety of competitions were fixed.
"They all involve preliminary rounds of club competitions," Uefa spokesman William Gaillard told BBC Radio 5 Live.
And Gaillard described claims that England might get a back way into the Euro 2008 finals as "pure fantasy".
Some reports have suggested that the investigation could ultimately lead to England or Scotland - who both failed to qualify - getting places at next summer's finals.
"In most cases it is just suspicion," said Gaillard.
"There is only one match that involves an investigation and that was a match in the second round of the Intertoto Cup. It was not a decisive match."
"This is clearly very serious and potentially one of the most serious things that has happened in world football."
The BBC's sports news correspondent Nigel Adderley said: "Uefa's suspicions have been raised by unusual betting patterns.
"But history suggests that following the money is very difficult and, despite the scandal that rocked Italian football last year, cases where corruption has been discovered and proved are relatively rare."
The story was first reported in German magazine Der Spiegel.
The magazine alleges that the vast majority of clubs involved come from countries in eastern and south-eastern Europe, with Bulgaria, Georgia, Serbia, Croatia and the Baltics among those named.
Graham Bean, the former police officer who used to head up the Football Association's compliance unit, told BBC World Service: "They are exceptionally serious allegations if the stories are correct but they will be extremely difficult to investigate.
"Clearly Uefa, for them to pass this report across, do have some evidence of some kind that would suggest has come down the route of betting patterns or individuals rolling over and telling them what they know.
"Nevertheless if that is the case they still need to get corroborative evidence to prove what has supposedly gone on.
"If the evidence is there and football wants to take this on and deal with this properly with the police, then the simple fact is the punishments that should be imposed on any clubs or individuals found guilty should be extremely excessive.
"There is so much money involved now, not only in football but in the betting industry, whereby you can get a bet on anything, it clearly opens it up to corruption if a betting syndicate can drop on the right person.
"I can't remember anything happening on this scale before.
"For something of this magnitude and these type of games then this is clearly very serious and potentially one of the most serious things that has happened in world football."
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