At least 39 people lost their lives after two high-speed trains collided near Adamuz, in the province of Córdoba, Spain.
The accident also injured dozens of people, while the investigation focused on the causes that led to one of the trains derailing.
According to preliminary reports, an Iryo train travelling from Málaga to Madrid derailed and collided with another train operated by the state-owned company Renfe, which was moving in the opposite direction. The collision also caused the carriages of the second train to derail, and some of them fell onto a steep embankment.
One of the lines being examined by investigators was the possibility of a defect in a rail joint. According to sources cited by Reuters, a damaged section of this joint was found at the scene, which may have created a gap between the rail segments.
However, authorities stressed that the final cause of the accident must be determined by the technical investigation.