KHARAGPUR: The official investigation into India's deadliest rail crash in over two decades began on Monday after preliminary findings pointed to signal failure as the likely cause for a collision that killed at least 275 people and injured 1,200.

The disaster struck on Friday, when a passenger train hit a stationary freight train, jumped the tracks and hit another passenger train passing in the opposite direction near the district of Balasore, in the eastern state of Odisha.

Following non-stop efforts to rescue survivors and clear and repair the track, trains resumed running over that section of the line on Sunday night.

Trains were passing slowly by the derailed and mangled compartments, while repair work continued at the track side.

Some 120 km (75 miles) further north, at Kharagpur in West Bengal state, railway officials and witnesses gathered to submit evidence to a two-day inquiry, led by A.M. Chowdhary, commissioner of railway safety for the south-eastern circle.

"Everyone involved at the site have been asked to join the inquiry. The probe will take time and we are looking at all possible angles," Chowdhary told reporters.

India's Railway Board has recommended that the federal Central Bureau of Investigation (CBI) take over the probe into the cause of the disaster.

Chowdhary said he will submit his report to the Railway Board while the CBI investigation could run simultaneously.

Railway police also filed a complaint, seen by Reuters, without naming anyone under the Indian Penal Code sections dealing with causing "grevious hurt" or "endangering life" by negligence.

Preliminary investigations indicated the Coromandel Express, heading southbound to Chennai from Kolkata, moved off the main line and entered a loop track – a side track used to park trains – at 128 kph (80 mph), crashing into the stationary freight train.

That crash caused the engine and first four or five coaches of the Coromandel Express to jump the tracks, topple and hit the last two coaches of the Yeshwantpur-Howrah train heading in the opposite direction at 126 kph on the second main track.

At state capital Bhubaneswar's biggest hospital, the All India Institute of Medical Sciences (AIIMS), authorities set up large television screens with pictures of the dead to help desperate families who are scouring hospitals and mortuaries for friends and relatives.

Pradeep Jena, chief secretary of Odisha, told reporters that 170 bodies had so far been identified, more than half of the total toll.

Others were still searching for their relatives.

"We've checked all the hospitals but couldn't find the body. We are really exhausted," said a man, displaying a picture of his missing cousin Anjarul Hoque.

There was also an incident of a double claim for a dead body at the hospital in Bhubaneswar.

Afuy Shaikh and Dilip Kumar Sabar both sought to claim the body with tag number 63. Police officials said that a DNA test would be required if identification was inconclusive.

"We have to move towards normalization... Our responsibility is not over yet," said railway minister Ashwini Vaishnaw, his voice choking with emotion.

The Chennai-bound Coromandel Express was due to resume running on Monday for the first time since the accident but the service was cancelled shortly before departure.

Aditya Chaudhary, chief public relations officer of South Eastern Railway, said this was due to a shortage of train coaches.