Spanish Prime Minister Pedro Sanchez has promised to find out the cause of a deadly high-speed train crash in southern Spain that killed at least 40 people. The crash happened on Sunday evening near Adamuz when a Madrid-bound train derailed and collided with another train coming from the opposite direction. Over 120 people were injured. Rescue teams are still working to save passengers trapped in the wreckage. Sanchez visited the site and announced three days of national mourning for the victims. The accident is the worst Spain has seen in more than ten years. The crash occurred at 19:45 local time, about an hour after a train left Malaga heading to Madrid. The second train was traveling from Madrid to Huelva. Transport Minister Óscar Puente said most victims were in the front carriages of the second train. Investigation experts found a faulty joint on the rails may have caused the accident. Rail operator Adif said 400 passengers and staff were on board both trains. Of those injured, 41 remain hospitalized, with 12 in intensive care. The official death toll may rise as identification continues. Emergency services and the Spanish Red Cross are providing support and counselling to victims and their families. High-speed train services between Madrid and southern cities have been paused until Friday. King Felipe VI and Queen Letizia expressed deep concern and condolences. Spain's high-speed rail network is the second largest worldwide, stretching over 4,000 km. The crash recalls the 2013 rail disaster in Galicia, which caused 80 deaths.