The Swiss captain is not shy of a booking, having been cautioned 52 times in the Premier League since joining from Borussia Monchengladbach in 2016.
But his controversial yellow card against Leeds on 18 December is under scrutiny as part of a probe into suspicious betting activity.
Arsenal beat Leeds 4-1 at Elland Road, with Gabriel Martinelli bagging a brace and Bukayo Saka and Emile Smith-Rowe both on target.
Xhaka was shown a yellow by referee Andre Marriner in the 86th minute for timewasting, having spent around 20 seconds delaying a free-kick in his own half.
A mammoth bet of around £52,000 was placed for Xhaka to be booked in the final ten minutes of the game, with the payout coming in at £250,000.
In January, a month after the incident, the FA confirmed they had launched an investigation after being alerted by bookmakers.
And according to the Daily Mail, the case is now with the UK's main organised crime agency. There is no investigation into Xhaka's conduct and neither he or any of his teammates are believed to have done anything wrong.
Instead, the issue is more to do with the unusually hefty sum placed for a yellow card related wager and the fact it was done on a betting exchange where punters can swap stakes.
The odds for a yellow card being brandished in the last ten minutes were also much higher than when the game began.
Xhaka was yellow carded 10 times last season and was also sent off on two occasions.
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