With rescue work finished, authorities began clearing the mangled wreckage of two passenger trains that derailed in eastern India, killing more than 300 people and injuring hundreds.

On Sunday officials said the accident was the country’s deadliest rail accident in decades.

Investigators are looking into possible causes behind Friday night’s crash in Balasore district of eastern Odisha state, including whether human error or signal failure played a role.

Fifteen bodies were recovered on Saturday evening and efforts continued overnight as heavy cranes were used to remove an engine that had settled on top of a rail car.

No bodies were found in the engine and the work was completed on Sunday morning, said Sudhanshu Sarangi, director-general of fire and emergency services in Odisha.

The accident occurred at a time when Prime Minister Narendra Modi is focusing on the modernisation of the British colonial-era railroad network in India, which has become the world’s most populous country with 1.42 billion people.

Despite government efforts to improve rail safety, several hundred accidents occur every year on India’s railways, the largest train network under one management in the world.

Preliminary investigations revealed that a signal was given to the Coromandel Express to enter the main track line but the signal was later taken off.

The train entered another line, known as the loop line, and crashed into a goods train parked there, the Press Trust of India news agency reported.

When asked about the cause of the accident and preliminary findings, India’s Railways Minister Ashwini Vaishnaw said, “Let the inquiry report come out. It won’t be appropriate to comment.”

Chaotic scenes erupted on Friday night as rescuers climbed atop the wrecked trains to break open doors and windows using cutting torches to try to save people who were trapped inside the rail cars.

Mr Modi visited the crash site on Saturday to examine the relief effort and talk to rescue officials. He also visited a hospital where he asked doctors about the treatments being given to the injured, and spoke to some of them.

The Indian prime minister told reporters he felt the pain of those who suffered in the accident. He said the government would do its utmost to help them and strictly punish anyone found responsible.

Ten to 12 coaches of one train derailed, and debris from some of the mangled coaches fell onto a nearby track. The debris was hit by another passenger train coming from the opposite direction, causing up to three coaches of the second train to also derail, said Amitabh Sharma, a Railroad Ministry spokesperson.

Most train accidents in India are blamed on human error or outdated signalling equipment.

More than 12 million people ride 14,000 trains across India every day, traveling on 40,000 miles of track.