“We have identified the cause of the accident and the people responsible for it,” the minister said on Sunday, adding it was “not appropriate” to give details before a final inquiry report into the country’s deadliest rail disaster in decades.

There was confusion about the exact sequence of events leading to the crash in Balasore district in Odisha state.

But Jaya Verma Sinha, a senior railway official, said the preliminary investigations revealed that a signal was given to the high-speed Coromandel Express to run on the main track, but the signal later changed, and the train instead entered an adjacent loop line where it rammed a freight train loaded with iron ore. The collision flipped Coromandel Express’s coaches onto another track, causing the incoming Yesvantpur-Howrah Superfast Express from the opposite side also to derail, she said.

The passenger trains, carrying 2,296 people, were not overspeeding, she said. Trains that carry goods are often parked on an adjacent loop line on the side so the main line is clear for a passing passenger train.

Sinha said the root cause of the crash was related to an error in the electronic signalling system. She said a detailed investigation will reveal whether the error was human or technical.

The electronic interlocking system is a safety mechanism designed to prevent conflicting movements between trains. It also monitors the status of signals that tell drivers how close they are to the next train, how fast they can go and the presence of stationary trains on the track.

“The system is 99.9 percent error-free. But 0.1 percent chances are always there for an error,” Sinha said. To a question whether the crash could be a case of sabotage, she said, “Nothing is ruled out.”

“Whatever information there is it is not a complete investigation. These are preliminary investigation. They still need to investigate what went wrong,” Al Jazeera’s Um-E Kalsoom Shariff, reporting from Balasore, said.

Families scoured hospitals and morgues

Authorities worked to clear the mangled wreckage of the two passenger trains, as families scoured hospitals and morgues for missing relatives.

Al Jazeera’s Shariff said volunteers have set up camp to provide transport and food to people looking for their loves ones. “People with serious injuries have been moved to other cities [such as Cuttack] where there are bigger hospitals,” Shariff said.

On Sunday, a few shattered carriages, mangled and overturned, were the only remnants of the tragedy. Railway workers toiled under the sun’s glare to lay down blocks of cement to fix the broken tracks. A crew with excavators was removing mud and debris to clear the crash site.

Fifteen bodies were recovered on Saturday evening and efforts continued overnight with heavy cranes being used to remove an engine that 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 crash occurred at a time when Prime Minister Narendra Modi’s government is focusing on the modernisation of the British colonial-era railroad network in India, which has become the world’s most populous country with estimated 1.42 billion people.

Despite government efforts to improve safety, hundreds of accidents occur every year on India’s railways, the fourth largest train network in the world. About 22 million people ride 14,000 trains across India every day, travelling on a network of 64,000km (40,000 miles).

Modi visited the crash site on Saturday and talked to rescue officials. He also visited a hospital to inquire about the injured and spoke to some of them.

Modi told reporters he felt the pain of the crash victims. He said the government would do its utmost to help them and strictly punish anyone found responsible.

In 1995, two trains collided near New Delhi, killing 358 people in one of the worst rail accidents in India. In 2016, a passenger train slid off the tracks between the cities of Indore and Patna, killing 146 people.

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