Villarreal and Getafe have denied any wrongdoing after Spanish media reported police are investigating possible match-fixing in a 2-2 draw between the two clubs in La Liga last year.
"Villarreal and its first team wish to show their absolute rejection of the accusations made today and categorically deny being involved in any way in fixing the game against Getafe on the final day of last season," read a club statement.
"As it has done on repeated occasions, the club condemns any conduct that damages the essence of sport and competition and stresses that the values of transparency, ethics, integrity and fair play are fundamental to its philosophy."
Getafe also released a statement saying the club "wish to categorically deny any involvement with this matter and this type of conduct".
Newspaper El Pais reported the match was being looked at as part of Operation Oikos, which was launched last year and led to 11 people being arrested on suspicion of forming a match-fixing group to profit from betting on games.
La Liga confirmed it had opened a confidential dossier as part of Operation Oikos but added details of the case would not be made public until it goes to trial.
The court based in the city of Huesca that El Pais said was investigating the case could not be reached for comment.
"Operation Oikos came about due to an accusation by La Liga, which has joined the case as a private plaintiff, and will take all legal measures necessary to clarify the facts that are under investigation," La Liga said in a statement.
Getafe had to beat Villarreal to stand a chance of qualifying for Europe's elite Champions League club competition ahead of Valencia. Villarreal had nothing to play for.
Valencia's 2-0 win at Real Valladolid on the same day, however, meant that in the event Getafe could not have qualified for the Champions League even if they had beaten Villarreal.
Five former Osasuna directors and two former Real Betis players were given jail sentences last month following an investigation into match-fixing in 2013 and 2014, the first convictions for sporting corruption in Spanish football.