Cardiff have urged the French authorities to launch an official investigation into the death of striker Emiliano Sala.
Argentinian forward Sala died on January 21, 2019 when the plane carrying him from Nantes in France to his new club Cardiff crashed in the English Channel near Guernsey.
Cardiff have responded to an article published in French sports newspaper L'Equipe, which claimed Nantes owner Waldemar Kita and the player's agent, Willie McKay, were central to any potential investigation.
A Cardiff spokesperson said: "CCFC has been clear throughout the past 12 months that a full investigation of the facts leading up to the tragedy is required.
"Not only to fully understand what led to the downing of the Piper PA-46 Malibu plane, but to answer the wider questions that have been highlighted in this case, specifically related to the use of illegal flights in the football industry and the role of intermediaries in player transfers.
"As a result of our investigation we believe there is sufficient evidence of wrongdoing that necessitates investigation by the French authorities of those responsible for the arrangement of the transfer on behalf of FC Nantes and for arranging the doomed flight.
"We have therefore passed over information to the Parquet de Nantes to assist their efforts. We remain committed to establishing the full facts and adhering to any final decision on our financial liability in the transfer."
Sala's body was recovered from the wreckage, but pilot David Ibbotson, from North Lincolnshire, has still not been found.
Sky Bet Championship club Cardiff, who were in the Premier League at the time, and Nantes have since been in dispute over fee payments.
Cardiff unveiled Sala two days before his death, but have argued they were not liable for the full £15million transfer fee because the 28-year-old was not officially their player when he died.
The case was heard by FIFA's players' status committee, with the world governing body announcing at the end of September that Cardiff had been ordered to pay the first instalment of Sala's transfer fee – six million euros (just under £5.2m).
Cardiff appealed against that ruling and it will go before the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland. The final decision is not expected before June 2020.
Sala's father Horacio died three months after his son, suffering a heart attack at his home in Progreso, Argentina.
But he said before his death that all parties involved in the transfer – including clubs and agents – should have made more effort to look after the welfare of his son.
Sala was exposed to high levels of carbon monoxide prior to the crash, a report later revealed.
Cardiff management, players and supporters paid tribute to Sala last week on the first anniversary of his death.
Bluebirds manager Neil Harris, captain Sean Morrison and Sol Bamba were among those to attend a dedication service to Sala and Ibbotson last Tuesday at St David's Cathedral in Cardiff city centre.
Supporters arrived at the Cardiff City Stadium throughout the morning to pay tribute and left flowers, banners and shirts in memory of Sala.
