"I was asleep," an unidentified male survivor told NDTV news. "I was woken up by the noise of the train derailing. Suddenly I saw 10-15 people dead. I managed to come out of the coach, and then I saw a lot of dismembered bodies."
Video footage from Friday showed rescuers climbing up one of the mangled trains to find survivors, while passengers called for help and sobbed next to the wreckage.
The collision occurred at about 19:00 local time (1330 GMT) on Friday when the Howrah Superfast Express, running from Bangalore to Howrah, West Bengal, collided with the Coromandel Express, which runs from Kolkata to Chennai.
Authorities have provided conflicting accounts on which train derailed first to become entangled with the other. The Ministry of Railways said it has initiated an investigation into the incident.
Although Jena and some media reports have suggested a freight train was also involved in the crash, railway authorities have yet to comment on that possibility.
An extensive search-and-rescue operation has been mounted, involving hundreds of fire department personnel and police officers as well as sniffer dogs. National Disaster Response Force teams were also at the site.
On Friday, hundreds of young people lined up outside a government hospital in Odisha's Soro to donate blood.
According to Indian Railways, its network facilitates the transportation of over 13 million people every day. But the state-run monopoly has had a patchy safety record because of ageing infrastructure.
The state has declared Saturday a day of state mourning as a mark of respect to the victims.
India's deadliest railway accident occurred in 1981 when a train plunged off a bridge and into a river in Bihar state, killing an estimated 800 people.
