URDA: Prime Minister Pedro Sanchez on Friday (Oct 30) said Spain was working "tirelessly" to identify the 69 victims of this week's high-speed train collision as the anguish of distraught relatives grows.

Wednesday's crash in the central region of Castilla-La Mancha was Spain's second such disaster this year and one of Europe's deadliest rail accidents this century.

Relatives of the victims have endured an agonising wait for news as rescue crews sift through the wreckage of tangled metal and bodies are examined in morgues.

"All branches of the state are working tirelessly ... to try to give and provide the most information possible, as soon as possible, reliably, to the relatives of the victims," Sanchez said in the central city of Toledo, where most of the bodies have been taken.

Sanchez doubled down on a "commitment" to continuously inform the relatives, who have been providing DNA samples to the police to help the identification work.

Castilla-La Mancha's leader Emiliano Garcia-Page warned "we do not rule out there being more dead", saying the emergency services had collected "31 bags of partial remains" that complicated the identification work.

The legal authorities in charge of the process have said 70 reports for missing people have been presented. These could coincide with the bodies, all but five of which remain unidentified.

Many families are staying in Toledo, where an improvised morgue has been set up because the city's existing facility could not cope with all the corpses.

The accident occurred when a service by state operator Renfe ploughed into the back of a stationary train belonging to private Spanish company Iryo outside the village of Urda, around 130km south of Madrid.

The right-wing opposition is demanding the resignation of Socialist Transport Minister Oscar Puente for his handling of the rail network. He was due to hold a press conference on Friday.