The Premier League side are looking into all details of the deal to sign the striker, which is why they have yet to pay the first installment to Nantes.
Chairman Mehmet Dalman has promised Cardiff City will be an "honourable club" with Nantes over the payment of a transfer fee for Emiliano Sala, once they have gathered further information.
Striker Sala was heading to Cardiff after completing a club-record move from the Ligue 1 side when the Piper Malibu aircraft carrying both the player and pilot David Ibbotson disappeared on January 21.
The 28-year-old's body was recovered with the help of specialist contractors from the plane wreckage in the English Channel last week.
Reports emerged in France last Wednesday that Nantes were demanding the first instalment of the €15million Cardiff had agreed to pay for the Argentine forward.
Dalman insists the Premier League club will pay up - but not before they have investigated what they believe to be "anomalies" in the deal.
"Of course, if we are contractually obliged to pay them then of course we will. We are an honourable club," he told BBC Sport Wales.
"But if we are not - and there are some anomalies in that - then surely you would expect me as the chairman and guardian of this club's interests to look into that and hold our position? That is what we are doing.
"We are still in the process of gathering information and that process will be ongoing. And when we reach a level where we have enough information, I am sure we will sit down with Nantes and move forward."
Dalman also confirmed Nantes have threatened legal action, adding: "They have asked for what they believe is the money due to them and there is a process and they have initiated that process.
"What we are saying is that we are not in agreement with that process given the extraordinary events that have taken place and the tragic circumstances. We are not making any positive or negative statements.
"We are simply saying, please understand there are a lot of questions which need to be answered and that is what we are trying to do."