The Spanish Prime Minister promises to find the cause of the deadly high-speed train accident

Spanish Prime Minister Pedro Sanchez has declared three days of national mourning for the victims of a high-speed train crash that killed at least 40 people.

Sanchez also vowed to find out why the two high-speed trains collided in southern Spain as rescuers continue to search the wreckage.

More than 120 people were injured when carriages of a Madrid-bound train derailed and crossed onto the opposite track, colliding with an oncoming train in Adamuz on Sunday evening.

The crash is the worst the country has seen in more than a decade.

Rail network operator Adif said the collision occurred at 7.45pm local time (6.45pm GMT) on Sunday, about an hour after one of the trains left Málaga heading north to Madrid when it derailed on a straight stretch of track near the city of Córdoba.

According to Transport Minister Óscar Puente, the wagons of the second train were pushed against an embankment by the force of the crash. He added that most of the dead and injured were in the front carriages of the second train, which headed south from Madrid to Huelva.

Rescue teams said the twisted wreckage of the trains made it difficult to free people trapped in the carriages.

Sánchez visited the crash site with senior officials on Monday afternoon.

“This is a day of sadness for all of Spain, for our entire country,” he told reporters.

“We are going to find the truth, we are going to find the answer, and when that answer about the origin and cause of this tragedy is known, as it cannot be otherwise, with absolute transparency and absolute clarity, we will make it public.”

Puente said an investigation could take at least a month, describing the incident as “extremely strange.”

But news agency Reuters quoted an unnamed source briefed on the initial investigations as saying experts had found a faulty connection in the rails, causing the gap between track sections to widen as trains passed over them. They added that the joint was key to identifying the cause of the accident.

Spanish newspaper El País said it was not clear whether the malfunction was a cause or a consequence of the crash.

Four hundred passengers and staff were on board the two trains, railway authorities said. Emergency services treated 122 people, of whom 41, including children, were still in hospital. Twelve of them are in intensive care.

Puente said the death toll “is not yet final.” Officials are working to identify the dead.

The type of train involved in the crash was a Freccia 1000, which can reach top speeds of 400 km/h, a spokesman for Italian railway company Ferrovie dello Stato told Reuters.

Salvador Jimenez, a journalist at RTVE who was on one of the trains, said the impact felt like an “earthquake”.

“I was in the first carriage. There was a moment where it felt like an earthquake and the train had indeed derailed,” Jimenez said.

Images from the scene appear to show some train cars had tipped onto their sides. Rescuers can be seen climbing the train to pull people out of the crooked train doors and windows.

A Madrid-bound passenger, José, told public broadcaster Canal Sur: “There were people shouting and calling for doctors.”

All high-speed services between Madrid and the southern cities of Malaga, Cordoba, Seville and Huelva have been suspended until Friday.

King Felipe VI and Queen Letizia said they were following the news of the disaster “with great concern” and expressed their “most sincere condolences”.

The emergency response organization in the Andalusia region has called on all survivors of the crash to contact their families or post on social media that they are still alive.

The Spanish Red Cross has deployed emergency services to the scene and is also offering advice to families in the area.

Miguel Ángel Rodríguez of the Red Cross told RNE radio: “The families are experiencing a situation of great anxiety due to the lack of information. These are very distressing moments.”

In 2013, Spain suffered its worst high-speed train derailment in Galicia, northwestern Spain, killing 80 people and injuring 140 others.

Spain’s high-speed rail network is the second largest in the world after China, connecting more than 50 cities across the country. Data from Adif shows that the Spanish railway line is more than 4,000 km long.