Uefa is investigating 40 cases of suspected match-fixing involving games in the Champions League and Uefa Cup.
The head of Uefa's disciplinary services Peter Limacher said they were looking at early qualifying matches.
The games are from the last four years, with 15 in the last two years, and mainly involve Eastern European teams.
In April this year Macedonian club FK Pobeda received an eight-year ban from European competition after being found guilty of deliberately losing a match.
Since then, Uefa has announced three Macedonian clubs were being investigated.
One of the fixtures under suspicion is Macedonian side FK Milano's 12-2 aggregate loss to Croatia's Slaven Koprivnika in the second qualifying round of the Europa League, the new format for the old Uefa Cup.
"Right now it's mainly Eastern Europe clubs being investigated," said Limacher.
"They know they are not going to be involved later in the tournament and they are going out, so decide, 'Let's make a profit'.
"In the cases we have seen it's really the deliberate planned fix of the games, the whole games. First the result at halftime then after 90 minutes.
"It might take some time (to convict) but in cases where we can work together with the police that might be possible."
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