Manchester United have launched an investigation into claims that their dressing room was bugged during the Premiership victory over Chelsea.
Ferguson's pre-match team talk is apparently included on the tapes
Audio tapes apparently recorded at Old Trafford were obtained by The Sun, which handed them to the club.
A club statement said: "We have launched our own investigation and if necessary will involve the police."
The tapes apparently contain recordings of pre-match and half-time team talks, plus celebrations after the 1-0 win.
Manager Sir Alex Ferguson had been under pressure before the game after United's 4-1 Premiership defeat to Middlesbrough and a 1-0 reverse to Lille in the Champions League.
On the tapes, Ferguson can reportedly be heard giving an inspirational team talk to his players before the game, and then issuing tactical advice at half-time when his side led 1-0.
In the wake of the victory, which ended Chelsea's 40-game unbeaten run, United's players are recorded congratulating each other.
The tapes also feature the players' reactions to Ferguson's post-match interview on television and then Chelsea boss Jose Mourinho's.