Sala and pilot David Ibbotson were onboard a private aircraft, the wreckage of which was discovered on Sunday evening underwater in the English Channel.
The Ligue 1 club have demanded payment from Cardiff, according to BBC Wales, but the Bluebirds are withholding fees until they are satisfied with the documentation concluding Sala’s disappearance.
However, Nantes are demanding an initial payment of £5m (R87m) is transferred immediately for Sala, who is missing presumed dead after the wreckage was found.
According to Sky Sports News, Cardiff have not yet paid any of the £15m fee agreed for the Argentine striker.
The transfer fee is reportedly set to be paid over three instalments, and Cardiff are reportedly surprised that Nantes have requested the money while Sala has still not been officially found.