Nine people appeared in the Kempton Park magistrate's court on Tuesday for the theft of millions of US dollars from Johannesburg International Airport, SABC news reported on Tuesday.
Their telephone conversations with each other could be used to link them to the crime, investigating officer Peter Mbonani testified in their bail application.
Lawyers representing the men have questioned whether the recordings were legally obtained.
Three of the men are Airports Company South Africa officials, who were suspended after their arrest. Two are foreign nationals arrested at South Africa's Beit Bridge border post with Zimbabwe two hours after the robbery.
On March 25, gunmen held up guards at the airport gates. Others armed with AK-47 assault rifles held up guards and police at a South African Airways aircraft and helped themselves to bags of currency flown in from Britain. - Sapa