The first carcass was discovered on Saturday morning, said police spokesperson Adele Myburgh.
"The owner of the game park... went to inspect the camp. He stumbled upon the (carcass) of a white rhino bull with an estimated value of R1m.
"The horn was removed, and the carcass was still quite fresh."
Myburgh said the bull was worth so much because it had been used for breeding.
A helicopter combing the area spotted another rhino carcass, she said on Sunday. This white rhino bull was worth about R350 000 and had also had its horn removed.
Another two wounded rhino cows were spotted from the helicopter.
"Their horns had not been removed, but they had been shot and wounded. They will have to shoot (one of the cows) because it's very badly injured."
The other cow was proving difficult to track down because she was frightened.
No arrests had been made.
In Limpopo on Saturday, one man was arrested after a rhino was shot and killed on a farm in Naboomspruit. Police spokesperson Lieutenant Colonel Ronel Otto said a farmer and his workers were patrolling the farm when they heard gunshots just after 05:00.
"They went to investigate and found a dead rhino that had been shot."
More than 20 people have been arrested countrywide in separate cases involving rhino poaching since September.
At least 210 rhinos have been killed for their horns since the beginning of this year - up from a total of 122 poached last year.
Black-market demand for rhino horns has risen sharply as economic growth has spread through east and south-east Asia, where the horn is falsely believed by some to have medicinal properties.