About 39 people were killed and more than 70, injured in Spain, when trains collided, on Sunday evening, at around 19:45.
Oscar Puente, Minister of Transport in Spain, said the cause of the accident is still unknown.
He also said the accident was “strange.”
A train to Madrid crossed into another track to crash onto an oncoming train, in Adamuz.
The train that went off the rails belongs to a private company, Iryo, while the other is a state asset, belonging to Renfe.
Iryo said there were about 300 people on its train when the accident occurred.
“Iryo deeply regrets the incident and has activated emergency protocols” the company said in a statement.
Renfe suspended trips between Madrid and Andalusia until further notice but said commercial services between Madrid, Toledo, Ciudad Real and Puertollano would proceed as scheduled.