In the town of Adamuz, Spain is observing a somber three-day mourning period following a tragic train accident in the southern region. Flags across the country flew at half-mast on Tuesday as emergency teams continued their search for additional victims.

The death toll from Sunday’s catastrophic event has climbed to 40, but authorities caution that this figure might rise. Andalusian regional president Juanma Moreno described the scene as a “twisted mass of metal,” with rescue teams still combing through the wreckage for more bodies.

Spain’s Interior Minister, Fernando Grande-Marlaska, speaking to national broadcaster RTVE on Monday night, revealed that rescuers have located three more bodies within the debris. However, these have not yet been added to the official casualty count.

The disaster struck at 7:45 p.m. on Sunday when a train, carrying 289 passengers from Malaga to Madrid, derailed and collided with another train on its way from the capital to Huelva. Rail operator Adif confirmed the details of the collision.

The front section of the second train, which held nearly 200 passengers, bore the full force of the crash. This impact caused its first two carriages to derail and tumble down a 4-meter (13-foot) embankment. Moreno noted that some bodies were discovered hundreds of meters from the crash site.

Officials are continuing to investigate the causes of the incident that Spanish Transport Minister Óscar Puente has called “strange” since it occurred on a straight line and neither train was speeding.

But Puente said late Monday that officials had found a broken section of track.

“Now we have to determine if that is a cause or a consequence (of the derailment),” Puente told Spanish radio Cadena Ser.

Spanish Prime Minister Pedro Sánchez visited the accident site near the town of Adamuz on Monday, where he declared three days of mourning with flags lowered on all public buildings and navy vessels. Spain’s King Felipe and Queen Letizia are scheduled to visit on Tuesday.

Meanwhile, Spain’s Civil Guard is collecting DNA samples from family members who fear they have loved ones among the unidentified dead.