Viduka went back to his native Australia immediately following the pounds 3m deal, claiming that he was too stressed to play. Despite the demands of Zagreb and promptings from Uefa, European football's governing body, the Celtic owner, Fergus McCann, refused to pay Viduka's transfer fee, although it now appears that he feared he was being set up.
One newspaper reported that the player himself warned McCann that part of the cash would go directly to officials of the Croatian club. The paper claimed to have a copy of a letter signed by the Celtic director Fergus Sweeney which proves the Parkhead club called for a senior police investigation into the deal.
The letter stated: "My club is understandably disturbed at the events surrounding Viduka's transfer, and the depths of its concern can be gauged by the fact that the circumstances have been reported for investigation to the British police with a view to ascertaining whether there are any fraudulent elements in those circumstances. Viduka has advised Celtic that certain Croatian officials will receive part of this fee."
The letter is believed to have been lodged with world football's governing body, Fifa, although following initial inquiries the police could find no wrongdoing to substantiate Celtic's fears.
Zagreb have so far received pounds 900,000 for a player who has scored four goals in his first two games for Celtic. A final ruling on Viduka's transfer is expected from Fifa later this week.
The Dundee midfielder Dariusz Adamczuk, who was sent off in Saturday's defeat by Dunfermline, has been banned for six games by the Scottish Football Association.
A report from the referee Hugh Dallas has disclosed that Adamczuk was given two red cards, the first for a second booking and the second for his remarks to the referee. This meant he was automatically suspended for two games and, as he passed the 16-point threshold, an extra four games were added.
Adamczuk will not be back until the final three games of the season as Dundee struggle to avoid relegation from the Premier League.