The Hawks are investigating multiple instances of tampering at a Transnet fuel pipeline on the road to Koppies Dam in Bloemfontein.
"The suspects drilled their way into the pipeline, which passes through the grounds and funnelled fuel via a three metre pipe which was covered with grass. The fuel was then allegedly pumped into the trucks," the Hawks said in a statement on Wednesday.
It is unclear how many litres of fuel was stolen and the value thereof. It appears that the theft and tempering has been taking place for quite some time.
The theft was discovered on Tuesday after a Transnet security guard reported it to his superiors who in turn informed the local police about damaged infrastructure.
The impact led to pressure fluctuations and a drop on the pressure line.
"There has been reports of tampering to fuel lines especially in Mpumalanga, Gauteng, Free State just to name a few and investigations are ongoing," the Hawks said.
Members of the public with any concerns about suspicious activity, such as excavation taking place at an unusual time or at an odd location are urged to contact the police on 0860010111 or via MySAPS app.
The Hawks, together with the Local Criminal Record Centre, are investigating the matter.