A Chinese spectator at Sixfields stadium was detained over allegedly sending text messages to an foreign betting syndicate.
Sussex Police stepped in during the Coventry City versus Crawley Town match in on Sunday and the man was spoken to by the FA Fraud unit.
A Sussex Police spokeswoman said: “The man was spoken to in relation to alleged overseas betting syndicate fraud. He was not arrested and was not linked to any club.
“This is part of an ongoing investigation by the FA into betting syndicate fraud and Northampton and Sussex Police officers were there to support the FA fraud team in dealing with the man and obtaining his information.”
It is not known what was suspicious about the man’s texts.
However a common betting scam is to send details of events during professional matches across the world, so gangs can take advantage of the minute time delay between live action and TV coverage by placing bets on the information.