Peter Limacher, UEFA's head of disciplinary services, told a conference in London that the number of matches under investigation by UEFA for suspected match-fixing has reached 40 cases, it has been revealed.
He added that most of the cases were from eastern Europe and involved the early qualifying rounds of the Champions League and UEFA Cup.
A year ago the number of games being investigated was 25, and UEFA announced they were to set up a six-man special investigation unit to look into corruption in their competitions.
Limacher told the World Sports Law Report conference that there were now 40 games where suspicious betting patterns had been identified, 15 of those in the last two years.
Limacher said: "It is mainly clubs from eastern Europe that are being investigated."
In April, the Macedonian club FK Pobeda were banned from European competition for eight years by UEFA after being found guilty of match-fixing against Armenian side FC Pyunik in 2004 - they lost 3-1 at home in a Champions League first qualifying round.
FK Pobeda's president Aleksandar Zabrcanec was banned for life from any football-related activity, as was the player Nikolce Zdraveski.