A train travelling from Madrid to Seville hit a stationary train near the town of Orgaz in central Spain on Wednesday morning, killing at least 68 people and injuring dozens more, according to the BBC.

The collision happened just after 09:00 local time (08:00 GMT), about 140km (87 miles) south of Madrid, between the municipalities of Mora and Orgaz. The force of the impact sent several carriages down an embankment, and one carriage caught fire. Pictures published by the BBC show a long piece of railway track speared through one of the carriages. Some passengers said the piece of track that speared through a carriage may have slowed the train down. The Civil Guard's request for DNA samples from relatives points to the difficulty of identifying some victims, a process that can take days.

Spain's Transport Minister Óscar Puente said a computer failure followed by human error caused the crash. He described it as one of the worst rail disasters in Europe's modern history and Spain's deadliest in 13 years.

What the two trains were doing

The stationary train was operated by Iryo, a private rail company. It had 147 passengers on board and had stopped on the tracks because of a computer failure, Puente said. The moving train was operated by Renfe, Spain's state-owned railway company, and was carrying 397 passengers. Iryo said its train was struck from behind.

Puente's account focuses on the control room. When a system failure occurs, he said, a 24-hour control centre in Madrid takes over. That centre made what he called an "inexplicable" decision to instruct the trains to move again, without any speed restrictions. The minister's account is the most detailed official explanation so far, and investigators have not published their own conclusions.

What passengers described

Survivors described a violent, chaotic impact. Salvador Arriza, 62, who was on the Renfe train, told Reuters the force was "brutal" and that passengers began breaking windows to get out. "Some people couldn't move because they were trapped amongst the seats," he said.

Tangui Binier, 22, was on the Iryo train. He told the BBC that "suitcases started flying and people were screaming" when the train came to a halt. Outside, he saw the train "completely flipped over". He said his father carried a girl with a broken hip out of the wreckage, and he described seeing dead bodies and missing limbs. He also said the scene was hard to witness and that he did not know if he would ever recover.

Antonio Jiménez Barca, a journalist for El País, was walking towards the Renfe train's cafeteria when the crash happened. "I felt like I was being pushed from behind, like I was being thrown to the ground," he said. "I hit my head horribly... I was covered in blood."

Sebastián Herrero, 46, told El Mundo he saw "many people with broken noses, broken arms" and that he was "in the air for about four or five seconds". One survivor told a local television station that a woman died in his arms; the presenter also began to cry, according to the BBC.

The emergency response

Dozens of ambulances reached the scene, and a helicopter evacuated the most seriously injured. Spain's Civil Guard said it would need DNA samples from relatives to identify some of the victims, a sign of how badly some remains were damaged.

Prime Minister Pedro Sánchez visited the site. "The whole of Spain is grieving," he said. "Lives have been shattered, families have been torn apart, the pain is immense."

Most political parties cancelled campaign events scheduled for Wednesday. The far-right party Vox was the exception. Its leader, Santiago Abascal, said his party would not take part in what he described as attempts to "use mourning to silence criticism" of the country's rail infrastructure.

The disaster immediately became political. The leader of the opposition People's Party, Alberto Núñez Feijóo, said Spain had a right to know what was happening with its infrastructure and that failures in the security system would be addressed "with the utmost firmness". The CSIF trade union called on the transport minister to resign, accusing him of "scapegoating" a traffic manager by blaming human error in the control room instead of taking responsibility.

A second crash in the same year

Spain was already dealing with the aftermath of a high-speed rail disaster near Córdoba in January that killed 46 people. That crash happened on the same line, though much further south.

Sánchez said it was "unacceptable" for Spain to have two serious train crashes in one year and promised to "get to the bottom of this" and establish whether there was negligence. Wednesday's crash is the worst in Spain since 2013, when 80 people died on the outskirts of Santiago de Compostela.

What is still unknown

The official death toll may change. The BBC reports at least 68 killed, and casualty figures in major disasters often move as rescuers reach wreckage and hospitals update their counts.

The investigation is at an early stage. Puente has given a public account involving a computer failure and a control-room decision, but that account has not been tested by an independent inquiry, and the reasons behind the centre's instruction have not been explained publicly. The report does not say how long the line will remain closed or which specific signalling or control systems failed.

Nor is it clear whether the stationary train's position was itself part of the failure. The BBC reports that the Iryo train had stopped because of a computer failure, and that the control centre then told the trains to move. How those two facts connect is the central question for investigators.

What happens next

The immediate priorities are the injured, the identification of victims and the reopening of one of Spain's main high-speed corridors. Political pressure is already building: the transport minister faces calls to resign, the opposition wants answers on infrastructure, and the government has promised a full accounting.

For readers following the story, the reliable account is the one officials and the BBC have published: a Madrid-Seville train hit a stationary train near Orgaz, at least 68 people died, dozens were injured, and the transport minister has pointed to a computer failure and human error in the control room. The cause remains under investigation.