Transnet technicians are preparing to drain a portion of the gas and petrol pipeline that caught fire earlier on Tuesday in Alberton, Ekurhuleni, according to Ekurhuleni Disaster and Emergency Services Management spokesperson Eric Maloka.
Maloka said a dam-type hole would be dug to catch the drained fuel so that it did not ignite.
While the primary fire - a combination of gas and petrol within the pipeline - is under control, a secondary fire caused by the spillage of fuel is still burning.
Maloka said firefighters would use foam to blanket the fuel spill to contain it.
The fire broke out earlier on Tuesday as a result of attempted theft, Transnet CEO Sibongiseni Khathi said in a statement.
The area was evacuated and no injuries or fatalities were reported.
"Transnet pipelines have experienced an unprecedented spate of theft incidents on our pipelines and the associated infrastructure during the last few months," Khathi said in the statement.
"The latest incident occurred on the 31st December 2019 in Alberton, where an attempted theft incident at a block valve occurred on our Durban to Johannesburg petroleum pipeline, between Alrode and Airport, which has resulted in petrol spillage and fire," Khathi said.
He added that the theft and damage to high-pressure pipelines resulted in fires, asset damage and environmental risks, which bear "excessive remediation costs".
The pipeline was one of Transnet's 3 800km, high-pressure petroleum and gas pipelines, which runs from Durban to Gauteng. Maloka said only a portion of the pipeline would be drained.