BHUBANESWAR, INDIA -- Families of the victims of India's deadliest train crash in decades filled a hospital in Bhubaneswar city on Monday to try to identify the bodies of relatives, as railway officials recommended a criminal probe of the crash that killed 275 people.

Distraught relatives of passengers killed in the crash Friday lined up outside the eastern city's All India Institute of Medical Sciences. Meanwhile, survivors being treated in hospitals said they are still trying to make sense of the horrific disaster.

Outside the hospital, two large screens cycled through photos of the bodies, the faces so bloodied and charred that they were hardly recognizable.

Each body had a number assigned to it, and relatives stood near the screen and watched as the photos changed, looking for details like clothing for clues.

Many of the people said they spent days on desperate journeys from neighbouring states, travelling on multiple trains, buses or rented cars to identify and claim bodies, a process that stretched into a third day.

So far only 45 bodies have been identified, and 33 have been handed over to relatives, said Mayur Sooryavanshi, an administrator who was overseeing the identification process at the hospital in the capital of Odisha state, about 200 kilometres (125 miles) south of the site of the train crash in Balasore.

"It's the first time I have dealt with something like this," said Dr. Utkal Keshari Suna, a senior resident at the Bhubaneshwar hospital. "It's been a very difficult experience. I am in forensics, so I am used to dealing with dead bodies, but nothing like this," he said, standing inside the mortuary, where the air was thick with the smell of the dead.

"It's horrific. Time has also passed, so many bodies have started decomposing, so it's becoming more and more difficult to identify them," he said.

Upendra Ram began searching for his son, Retul Ram, on Sunday after travelling about 850 kilometres (520 miles) from neighbouring Bihar state. The day-long journey in a rented car, which cost him 35,000 rupees (US$423), was exhausting for Ram. Retul, 17, had been on his way to Chennai to find work, Ram said.

After spending hours looking at photographs of the dead, Ram identified his son around noon Monday.

"I just want to take the dead body and go back home. He was a very good son," said Ram, adding that Retul had dropped out of school to earn money for the family.

"My wife and daughter can't stop crying at home. They are asking me to bring the body back quickly," he said, wiping tears from his eyes with a red scarf he had tied around his head.

Friday's crash was one of the worst rail disasters in India's history. Investigators said a signaling failure might have been the cause of the disaster, in which a passenger train hit a freight train, derailing on the tracks before being hit by another passenger train coming in the opposite direction on a parallel track.

The collision involved two passenger trains, the Coromandel Express traveling from Howrah in West Bengal state to Chennai in Tamil Nadu state, and the Yesvantpur-Howrah Superfast Express traveling from Bengaluru in Karnataka to Howrah, officials said.

At least 123 trains scheduled to pass through Odisha were either canceled or delayed after the accident. The disruption led air fares to Odisha to spike, prompting India's civil aviation ministry to warn airlines over pricing surges.

Usman Ansari, who came from Bihar to collect the body of his brother-in-law, Kasim Mia, said he spent 24 hours on the road along with two friends. After reaching the site of the crash, they were told the bodies had been moved to Bhubaneswar.

They rented a car to drive to the hospital, where Ansari was finally able to identify and collect his brother-in-law's body.

"Kasim used to say he wanted to do everything for his children," he said, adding that compensation promised by the federal government would help take care of the man's four young children.

Authorities recommended on Sunday that India's Central Bureau of Investigations, which probes major criminal cases, open an investigation into the crash.

Some train traffic was restored Sunday evening on the tracks where the crash happened, after two days of repair work in which hundreds of workers with excavators removed the mangled debris of the trains.

The crash occurred as Prime Minister Narendra Modi is focusing on the modernization of India's colonial-era railroad network.

The South Asian nation has one of the world's most extensive and complicated railway systems with more than 40,000 miles (64,000 kilometres) of track, 14,000 passenger trains and 8,000 stations.

Spread across the country from the Himalayas in the north to tropical ports in the south, it has been weakened by decades of mismanagement and neglect. Despite efforts to improve safety, several hundred accidents happen every year.

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

In August 1995, two trains collided near New Delhi, killing 358 people in one of India's worst-ever train accidents.

In 2016, a passenger train slid off the tracks between the cities of Indore and Patna, killing 146 people.

More than 22 million people ride trains across India every day.

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Saaliq reported from New Delhi.