Audio file appears to point finger at control centre, but there are questions around signalling and technical issues

At least 69 people died when a high-speed train from Madrid to Seville hit another train on the same track from behind near Toledo on Wednesday morning.

Both trains had been brought to a halt earlier when the signalling system failed. The driver of the state-owned Spanish train, a Renfe AVE service, was told by controllers to restart the journey, but crashed into the train in front, run by the private operator Iryo. The front carriages of the AVE train and rear of the Iryo train were destroyed and others derailed.

Emergency services, drones and dog unit continue to comb carriages as Civil Guard sets up clinics for relatives to provide DNA samples

• How did the Spain train crash happen and what will investigators be asking?

Spain began three days of mourning on Thursday for at least 69 people who died in a high-speed rail collision, as hospitals continued to treat dozens of injured passengers and train drivers went on strike to urge more investment in railway safety.

The trains – one from Spain’s state-owned Renfe and the other from the private rail company Iryo – were travelling from Madrid towards the southern region of Andalucía on Wednesday when they collided just before 9am. After the Iryo train came to a halt, the other slammed into its rear, knocking several carriages off the track near Urda in the central region of Castilla-La Mancha.