Barcelona have denied that former president Sandro Rosell illegally bought a liver for ex-France defender Eric Abidal.
Abidal, 38, who is now the club’s technical secretary, had a transplant in 2012 after a tumour was found in his liver.
Barcelona say they “roundly deny any irregularity in the matter”.
The claim has also been denied by Abidal and the Hospital Clinic de Barcelona, where the player had the operation.
Barcelona added: “The club are saddened by the lack of rigor in the spreading of such information about such a sensitive issue.”
Spain’s national transplant organisation said it has started an internal investigation together with the hospital and the Catalan Transplant Organisation.
It said the information available showed the donation and transplant “was in accordance with current legislation and common clinical protocols”.
Abidal, who spent six seasons at the Nou Camp, made his comeback for Barcelona in April 2013 before joining Monaco three months later.
Last week a Spanish court ruled that Rosell, who is in custody, will stand trial on charges of money laundering involving the sale of television rights for Brazil matches.
Barcelona deny organ-trafficking claim