Emergency personnel and paramedics are working round the clock to free people trapped under the wreckage of two trains that collided before 09:00 at Mountain View station in Pretoria on Tuesday.
At least three people have been confirmed dead.
"Most unfortunately, as a result of the collision and the impact, we had three fatalities from this accident and more than 300 people that were seen by emergency services," Metrorail spokesperson Lillian Mofokeng told News24.
READ: At least three dead, scores injured in Pretoria train crash
Mofokeng said it was too early to determine the cause of the accident but said both trains had been travelling in the same direction and were on the same track when the accident happened.
She said Metrorail would institute an investigation into the crash.
Gauteng police spokesperson Major General Max Masha confirmed that an inquest had been opened.
"We are still going to investigate further and if we find that some people were negligent, a culpable homicide case will be opened and then we will take it from there," Masha said.
Meanwhile, Mofokeng said trains running on the Pretoria-Mabopane-Dewildt line were temporarily suspended until further notice.
"To make sure we manage this particular area, we have decided to close down the line and that means that we will not have train services operating between Pretoria and Mabopane, and between Ga-Rankuwa and Pretoria," Mofokeng said.
"All commuters in possession of valid weekly and monthly tickets will be transported by buses until the line is reopened".
Metrorail will set up a walk-in centre at Pretoria station for commuters who were involved in the accident and who need assistance.
"We urge commuters to bring the relevant documents with for processing," said Mofokeng.
She said Metrorail would support the families of the deceased and would visit the families later in the day.