Johan Smit, manager of SBV in Polokwane, said on Sunday the bodies of Marcus Malete, 25, Hennie Botha, 20 and Dirk Kleynhans, 28, would not be identified by their families.
They were burnt beyond recognition after a daring cash in transit heist between Marken and Baltimore, about 75km from Laphalale in the Waterberg region of Limpopo.
Deon Steyn, 20, a colleague, was rescued from the burning wreck, but apparently died because of smoke inhalation.
"The robbery was very bad. It is the first robbery in eight years our firm has been involved in", said Smit.
He said Kleynhans's wife, Colette, would find out on Monday whether she was pregnant. Rapport reported on Sunday that Steyn would have turned 21 in three months time.
The security guards from the SBV branch in Polokwane were on their way to Lephalale to take money to a bank.
An unknown number of robbers in a Mercedes-Benz, which was hijacked earlier in Pretoria, forced the van off the road. The robbers opened fire on the van after it had overturned.
They apparently failed to open the van and take the money boxes and then poured petrol over the van and the Mercedes.
They hijacked a passing motorist and left in three more getaway vehicles.
Neels Hennop, a farmer from the Marken area, who was first to arrive at the scene, said a pall of smoke and absolute silence hung over the scene when he arrived.
"I realised there must be people inside the van, but couldn't see or hear anything inside it. Complete silence hung over the place," said Hennop.
He said a worker from a nearby farm saw what had happened and was fired on by the robbers. He then raised alarm. Farmers in the area were informed about the robbery by two-way radio.
A group of them, among them Hennop, arrived at the scene.
"I battled to open the door of the van and fetched a pickaxe from by bakkie and broke the windscreen. I saw an unconscious man inside," said Hennop.
More farmers came to his aid and they managed to remove Steyn from the wreckage. Meanwhile some of the farmers had tried to resuscitate Steyn.
Two vehicles from Eskom happened to drive past and used their firefighting equipment to put out the flames.
"I broke the back window and saw three more people - They were lying near the sliding door and they were stiff: it was ugly," said Hennop.
He said the guards could not have survived long in the suffocating smoke.
"I breathed in some of the smoke and I was nearly lights out," he said.
Provincial police spokesperson for Limpopo, superintendent Ronel Otto, said nobody had been arrested in connection with the robbery.
Meanwhile, SBV has offered a reward of half a million rand for any information that would lead to the arrest of the robbers and their successful prosecution.