Prime Minister Pedro Sánchez announced the mourning period on Monday, calling the incident "a day of sorrow for all of Spain,” and pledged a thorough investigation into the cause of the crash. Speaking after visiting the scene with senior officials, Sánchez said the government would publish the findings "with absolute transparency and clarity” once the cause is established.

The collision occurred at 19:45 local time on Sunday near the town of Adamuz, rail infrastructure operator Adif said. A Madrid-bound train derailed on a straight section of track and crossed onto the opposite line, where it struck another high-speed service travelling from Madrid to Huelva. Transport Minister Óscar Puente said the force of the impact pushed several carriages into an embankment and that most of the deaths and serious injuries occurred in the front carriages of the second train.

Rescue workers faced significant challenges as they searched for survivors, citing twisted metal and unstable wreckage that made it difficult to access some carriages. Emergency services treated 122 people at the scene, while 41 remained in hospital, including 12 in intensive care. Authorities said around 400 passengers and staff were on board the two trains. Puente warned that the death toll may still rise as identification efforts continue.

An official investigation has been launched and could take at least a month, according to the transport minister, who described the incident as "extremely unusual.” Reuters quoted a source briefed on preliminary findings as saying investigators were examining a potentially faulty rail joint that may have created a widening gap in the track. However, Spanish newspaper El País reported that it remains unclear whether the defect caused the derailment or resulted from the crash itself.

The trains involved were Freccia 1000 models, capable of operating at very high speeds, according to a spokesperson for Italy’s state rail company Ferrovie dello Stato, which manufactures the trains. Rail authorities have suspended all high-speed services between Madrid and the southern cities of Málaga, Córdoba, Seville and Huelva until at least Friday as safety checks continue.

Passengers described scenes of panic and confusion. RTVE journalist Salvador Jiménez, who was travelling on one of the trains, said the impact felt "like an earthquake.” Another passenger, identified only as José, told regional broadcaster Canal Sur that people were screaming and calling for doctors in the immediate aftermath.

Footage from the scene showed multiple carriages tipped onto their sides, with emergency crews climbing over damaged wagons to help evacuate survivors. The Andalusian emergency agency urged those who escaped the crash to contact their families or post online to confirm they were safe, in an effort to reduce anxiety among relatives.

The Spanish Red Cross has deployed emergency response teams and is providing psychological support to victims and their families. "Families are going through moments of enormous distress due to the lack of information,” said Red Cross representative Miguel Ángel Rodríguez.

King Felipe VI and Queen Letizia expressed their condolences, saying they were following developments "with great concern” and offering sympathy to the victims and their families.

The crash is Spain’s deadliest rail disaster in more than a decade. In 2013, a high-speed train derailment in Galicia killed 80 people. Spain operates one of the world’s largest high-speed rail networks, spanning more than 4,000 kilometres and connecting over 50 cities nationwide.