Authorities said at least 38 passengers were killed when two express trains collided in southern Pakistan early Monday, as rescuers and villagers worked to pull injured people and bodies from the wreckage.

The pre-dawn collision occurred in Sindh province’s Ghotki district. According to Usman Abdullah, a deputy commissioner, the Millat Express train derailed and was quickly hit by the Sir Syed Express train. The cause of the derailment and subsequent collision was not immediately clear.

Cries for help pierced the darkness as survivors scrambled to escape and local villagers rushed to the scene to assist. As dawn broke, up to 20 passengers remained trapped in the wreckage of the Millat Express, and authorities were attempting to arrange heavy machinery to rescue those who remained trapped, according to Umar Tufail, the district’s police chief.

“The challenge for us is to rescue those passengers who are still trapped in the wreckage as soon as possible,” Tufail said. The death toll steadily increased throughout the morning, and Abdullah announced hours later that it had risen to at least 38. Dozens of people were injured.

Earlier, Azam Swati, the railways minister who was on his way to the crash site, told The Associated Press that engineers and experts were attempting to determine what caused the collision, and that all aspects would be investigated, including the possibility of sabotage.

According to railway officials, approximately 1,100 passengers were on board the two trains, and plans were being made to assist the survivors.

According to the military, troops are helping with relief and rescue efforts. According to the report, military doctors and ambulances were sent from a nearby city, and a team of military engineers was flown to Ghotki by helicopter.

According to local media, some of the passengers were on their way to a wedding party on the Millat Express train, but it was unclear whether they were among the dead or injured. Ambulances were seen transporting injured passengers to hospitals in television footage. Heavy machinery had not arrived at the scene four hours after the crash, according to Pakistani television stations.

The driver of the Sir Syed Express, Aijaz Ahmed, told Pakistan’s Geo News TV that when he saw the derailed train, he tried to avoid the accident by braking but failed. He didn’t say how he survived.

Some of the injured passengers were listed in critical condition at nearby hospitals. Malik Aslam, a local villager, told Pakistan’s Geo News TV that approximately 100 people had been injured and that he had counted at least 30 bodies while assisting with the rescue efforts.

Mohammad Amin, one of the Millat Express passengers who suffered minor injuries, told the Associated Press from a hospital that before the train left Karachi’s southern port city, he and his brother, who was also on board, saw railway mechanics working on one of the coaches.

This led them to believe there was a problem, but they were reassured that everything was fine. Amin claimed that the train car that was being worked on was the one that later derailed.

The chairman of Pakistan Railways, Habibur Rehman Gilani, told Geo News TV that the section of railway tracks where the accident occurred was old and needed to be replaced. He didn’t go into detail.

Train accidents are common in Pakistan, where successive governments have paid little attention to improving the aging signal system and deteriorating tracks.

In 1990, a crowded passenger train collided with a stopped freight train in southern Pakistan, killing 210 people in the country’s worst rail disaster.