At least 40 people have died and dozens more have been injured after two high-speed trains collided in southern Spain, local authorities have said.

The incident near the city of Córdoba has been described by local officials as Spain's worst rail crash in more than a decade.

Prime Minister Pedro Sánchez visited the scene on Monday, where he announced a three-day mourning period.

Here's what we know about the incident so far.

Where did the crash happen?

The crash occurred at around 19:45 local time on Sunday, about an hour after one of the trains departed Málaga for Madrid.

The train derailed and crossed over to the opposite track, operator Adif said.

It then collided with an oncoming train travelling from south Madrid to Huelva, which was forced into an embankment running alongside the track.

The majority of those killed and injured were in the front carriages of the Huelva-bound train, he added.

What caused the crash?

What caused the train to derail remains unclear.

Officials say an investigation has been launched but it is not expected to determine what happened for at least a month.

The president of Spain's state-owned rail operator, Renfe, has suggested a mechanical fault or infrastructure issue is a more likely cause rather than excessive speed or human error.

Are people still trapped in the trains?

There were around 400 passengers and staff on the two trains, operated by Iryo and Renfe, according to a statement from Renfe.

It is not clear if there are people still trapped inside the carriages but rescue teams are on site.

The president of the Andalusian regional government mentioned that heavy machinery is awaited to aid in lifting parts of the train that has suffered the worst damage.

Who are the victims?

The victims of the crash have not yet been identified, with officials stating that the death toll is not yet final.

As of Monday afternoon, 122 people had received medical assistance, 48 of whom remained hospitalized, local emergency services said.

What have the survivors said?

Passengers described the terrifying moments of the accident, likening the impact to an earthquake and detailing how the train's windows shattered, luggage flew around, and people were thrown to the ground.

Survivors are recounting an experience filled with screams and chaos as the trains collided, bringing a tragic end to what began as a routine journey.

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