Coroners were having difficulty identifying the eight French crash victims, including sailor Florence Arthaud, boxer Alexis Vastine and swimmer Camille Muffat, investigating judge Daniel Herrera said after he was handed the case on Wednesday.
He has given permission for French coroners to be invited to help.
Two Argentine pilots also died in the accident.
Herrera said that he would start interviewing the French witnesses – other crew and participants in the TV reality show Dropped that the victims were taking part in – on Thursday.
Two French psychologists have arrived in Villa Union, the town 30 kilometres from the scene of the accident where they are staying, to take over counselling from the medical team attached to the broadcast.
Technical experts from France’s air accidents investigation agency and the helicopters’ manufacturer inspected the scene for two hours on Wednesday and were to continue on Thursday and Friday.
A row has blown up in Argentina after it has emerged that the helicopters were public property leant to the production company by the two provinces involved.
Three opposition politicians claimed that the accident has revealed a little-known but frequent practise of lending the helicopters, which were bought for medical use, to TV companies and tourist operators.
La Rioja province governor Beder Herrera defended it on the grounds that it promoted tourism.