The SABC's Radio Park building in Auckland Park, Johannesburg, remains sealed off on Thursday as cleanup operations continue, following a diesel spill on Wednesday.
News24 reported that 2 000 litres of diesel had leaked from a generator on the 15th floor.
Employees were evacuated and were told to stay at home on Thursday, SABC spokesperson Vuyo Mthembu told News24.
Netcare 911 spokesperson Shawn Herbst said three patients suffered the effects of chemical inhalation and were treated on the scene before they were transported by ambulance to hospital for further assessment.
In a statement, the broadcaster said a power outage earlier on Wednesday morning had caused the SABC's internal systems to switch from City Power to a back-up generator.
"Due to the ageing and failure of the equipment, this led to the diesel tank overflowing," the statement read.
"The cleanup operation is still continuing [on Thursday] so employees will not be coming to work today," Mthembu said.
Mthembu said Radio 2000, 5FM and Metro FM would continue operating normally as their studios were on the ground floor of the building and were not affected by the spill.
"Contingency plans have been made for other radio stations to broadcast from other locations.
"For now, nobody will be allowed in [the contaminated] areas."
Mthembu could not estimate when the cleanup would be completed.
News24 reported that City of Johannesburg Emergency Services would remain at the premises until mopping up was completed and the building was declared safe.
EMS spokesperson Robert Mulaudzi said the 15th floor of the building was completely flooded and a no-go zone.
"Due to the nature of the risk which we might have, because the capacity of that standby generator is huge, there is a risk of a fire incident if we don’t manage it properly.
"Hence, we have decided that everyone who is inside the building must be evacuated so that we can monitor while the spillage cleaning services are busy," said Mulaudzi.
He said it was unknown when mopping up will be completed and EMS personnel will be on standby for any fires that may arise.
Concrete floors might be knocked out
A chemical spill cleanup expert, who does not want his name published, has told News24 that a cleanup of this nature could be laborious and complicated.
"Usually a hydrocarbon spill kit is used but for a spill of this nature, a large absorbent will have to be used. The biggest problem, though, is that the diesel will have seeped into the concrete. There is no way to extract the diesel from concrete. So that concrete will have to be knocked out and replaced. There is no other way.
"In terms of the walls, they will need to be replastered and repainted."
The expert said portions of the removed concrete would have to be tested for contamination. Only when the tests indicate that the concrete is clean, you can pour a new layer.
"If not, you would have to knock out more concrete until [the diesel] is completely gone. That is a requirement of the Department of Labour.
"Keep in mind, however, that this is a worst-case scenario."
Could be cleaned within a day
Johan van Vuuren, environmental manager at The Wastegroup, told News24 the effects of the spill might not be as bad, though.
"Diesel does not produce significant fumes because, basically, it's an oil. The problem with an oil-based contaminant is that it tends to penetrate.
"But it is relatively easy to clean up, depending on the type of surface. If the floor is tiled, for example, it can be cleaned up by an absorbent that looks like a blanket," Van Vuuren said.
Diesel is not much of a fire hazard either, Van Vuuren added.
"Diesel needs to be under pressure to ignite. If you use the right people, that spill can be cleaned in a single day," Van Vuuren said.