Rescue workers could be seen trying to cut their way into the mangled wreckage and television footage showed that the main section of one train carriage had been flung over an overhanging railway bridge.
The accident occurred when the Uttar Banga Express rammed into the stationary Vananchal Express, Saumitra Mohan, the area's district magistrate, said.
"Such was the impact of the crash that one coach was flung onto an over-bridge," Madan Lal, a railway ticket collector who reached the spot immediately after the accident, said.
More numbers at: IndianRailways.gov.in
||108,706km of track
||11,000 trains run every day; 7,000 are passenger trains
||1.54 million employees
||13 million passengers daily; 2 million tonnes of freight
"I could hear people crying and shouting in the dark," he told NDTV news channel.
"I was fast asleep on the top berth when there was this huge crash like an explosion," one passenger told the Times Now news channel.
"I was flung from the berth, and then people started shouting and there was complete panic," he said.
Mamata Banerjee, the railways minister, who is from West Bengal, told reporters before leaving for the accident site that "we have doubts in our minds about who is behind this accident".
"We are still finding out the details and we will take all necessary steps and action and find out who is behind this calamity," Banerjee said.
Compensation of 500,000 rupees ($10,500) was offered to the families of the dead and 100,000 rupees to the injured.
With a 108,706km network, the railways play a key role in Indian life, transporting more than 13 million passengers and more than 2 million tonnes of freight daily.
But the system is plagued by crowding and outdated technology.
This was the second major accident in the state of West Bengal within two months. In May, a train sabotage blamed on Maoist rebels killed more than 70 people. The rebels denied the charge.
Officials said any terror link in Monday's incident was unlikely, though an investigation was on to find out how both trains came to be on the same track.
There are 300 accidents on the railways every year, and past crashes have left hundreds dead.
In 2002, 100 were killed and 150 hurt when a carriage plunged into a river in the northeastern state of Bihar, while in 1995 more than 300 died in a collision near Ferozabad, close to the Taj Mahal city of Agra.
The worst accident on record dates back to 1981 when a train plunged off the track into a river in eastern Bihar state, killing 800 people.