Derby County have confirmed that police were contacted after a employee of Leeds United was caught "acting suspiciously" outside of their training ground.
The sixth-placed Rams are set to take on the Championship leaders on Friday in a clash of two teams with promotion aspirations.
But reports emerged on Thursday that a Leeds 'spy' had been spotted at Derby's training ground, with the club confirming the details in a statement on their wesbite.
"Derby County Football Club can confirm that officers from the Derbyshire Constabulary were called to the Derby County Training Centre at around 11:20am on Thursday 10th January, 2019, following reports of a man acting suspiciously outside the premises," it read.
"It has since been confirmed to Derby County that the individual concerned is an employee of the footballing staff at Leeds United Football Club.
"The club is now in discussion with Leeds United club officials in relation to this incident. At this time no further comment will be made."
Derbyshire Police took to Twitter to confirm the incident, saying that no damage was done and no arrests were made.
Marcelo Bielsa's Leeds have lost each of their last three matches in all competitions, tasting defeat to Hull City and Nottingham Forest in the Championship before suffering an FA Cup defeat to QPRs in Sunday's third-round fixture.
Despite that they remain two points clear of second-placed Norwich City in the league table as they aim to return to the Premier League for the first time since 2003.
Frank Lampard and Derby, meanwhile, sit eight points behind the league-leaders, but look set to challenge for at least a play-off berth ahead of Friday's meeting at Elland Road.
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