Rescue workers pulled 31 bodies from the wreckage, said Ashwini Srivastava, a spokesman for the railways.
The engine and two coaches of the Janata Express jumped off the tracks near Bachhrawan village in Uttar Pradesh state.
Several people were feared trapped in the wreckage, and rescue efforts were focused on bringing them out alive, said Ram Murath Yadav, a police official at the site of the accident.
One of the derailed coaches was crushed by the impact and most of the casualties were in that coach, he said.
The cause of the derailment was not immediately known. The federal rail ministry has ordered an inquiry.
The driver of the train escaped unhurt and was being questioned, Srivastava said.
Train accidents are common in India. The country's railroad network is one of the world's largest and carries more than 23 million passengers each day. Most accidents are blamed on poor maintenance and human error.
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