Spanish Prime Minister Pedro Sánchez promised to find out why two high-speed trains collided in southern Spain, killing at least 40 people, as rescuers continued to search for the wreckage.
After visiting the crash site, Sánchez also announced three days of national mourning for the victims.
More than 120 people were injured when a carriage on a Madrid-bound train derailed and crossed onto the opposite track, colliding with an oncoming train in Adamuz on Sunday evening.
The clashes are the worst the country has seen in the past 10 years.
Adif, the operator of the rail network, said the crash occurred at 19:45 a.m. (18:45 GMT) on Sunday. About an hour after one of the trains left Malaga heading north to Madrid, it derailed on a straight track near the city of Córdoba.
Transportation Secretary Óscar Puente said the force of the collision pushed a carriage on the second train into an embankment. He added that most of the dead and injured were in the front carriage of the second train, which was traveling south from Madrid to Huelva.
Rescue teams said the twisted wreckage of the train made it difficult to free people trapped inside the carriages.
Sánchez visited the crash site Monday afternoon with senior officials.
“Today is a day of sorrow for all of Spain and our entire country,” he told reporters.
“We will seek the truth and find answers. When the answers to the roots and causes of this tragedy become known with absolute transparency and clarity, we will make them public.”
Puente described the incident as “very strange” and said the investigation could take at least a month.
But Reuters, citing unnamed sources briefed on the initial investigation, said experts had discovered faulty joints in the tracks, which were causing gaps between sections of track to widen as trains passed by. They added that the joint was key to determining the cause of the accident.
Spain’s El Pais newspaper reported that it is unclear whether this accident was the cause or the result of the accident.
Railway officials said 400 passengers and staff were on board the two trains. Emergency services treated 122 people, of whom 41, including children, remain in hospital. Of these, 12 are in intensive care.
Puente said the death toll was “not yet confirmed.” Authorities are working to identify the deceased.
The type of train involved in the crash was a Freccia 1000, which can reach top speeds of 400 km/h (250 mph), a spokesman for Italian railway company Ferrovie dello Stato told Reuters.
RTVE reporter Salvador Jimenez, who was on the train, said the impact felt like an “earthquake.”
“I was in the first carriage. There was a moment where it felt like there was an earthquake and the train actually derailed,” Jimenez said.
Video from the scene appears to show some train carriages flipped on their sides. Rescue workers can be seen scaling the train to pull people out of its distorted doors and windows.
“People were screaming and calling for doctors,” Jose, a passenger heading to Madrid, told public broadcaster Canal Sur.
All high-speed services between Madrid and the southern cities of Málaga, Córdoba, Seville and Huelva were suspended until Friday.
King Felipe VI and Queen Letizia said they were watching news of the disaster “with great concern” and expressed their “most sincere condolences.”
Andalusia’s regional emergency agency urged all crash survivors to contact their families or post news of themselves alive on social media.
The Spanish Red Cross deployed emergency support services to the scene while also providing counseling to nearby families.
“Families are experiencing great anxiety due to lack of information. It is a very painful moment,” Miguel Ángel Rodríguez of the Red Cross told RNE radio.
In 2013, the worst high-speed train derailment occurred in Galicia, northwestern Spain, killing 80 people and injuring 140.
Spain’s high-speed rail network is the second largest in the world after China, connecting more than 50 cities across the country. According to Adif data, Spain’s railways are more than 4,000 km (2,485 miles) long.
