The collision occurred between a moving Zakaria Express and a stationary Fareed Express and they were looking at negligence as a possible cause as a stop signal appeared to have been ignored.
At least 20 people have been killed after a train collided with stationary coaches in Pakistan, hospital officials have said.
Television footage showed mangled and overturned carriages at the scene at the railway station in Karachi, Pakistan’s biggest city, as rescue workers tried to free people still trapped inside the wreckage.
A further 65 people are said to have been injured and a senior administration official said there could have been up to 1,000 people on board at the time of the crash.
Rescuers armed with metal cutting equipment and heavy cranes were joined by the military and the police.
