The fire broke out on Friday at a mine near Rustenburg, about 120 kilometres from Johannesburg, the owners said in a statement.
"The four employees were overcome by fumes while they were trying to find their way to safety," Impala said.
Minister for Mines Mosebenzi Zwani today said he was "very saddened by this tragic incident," adding: "The health and safety of workers is of paramount importance and should continue to be a priority in all operations."
The National Union of Mineworkers, the main union body representing the sector, today said it was "deeply concerned about these fatalities happening at Impala Platinum."
Fourteen gold miners died at the start of 2014 in an explosion and in 2009 nine workers at a platinum mine were crushed by falling rocks.
But there are many more accidents involving illegal miners. South Africa has approximately 6,000 mines that companies have abandoned in the face of falling profits.
