Rescuers in northern India are sorting through the wreckage of an express train that derailed, killing at least 20 people and injuring 100 more.

Authorities say the Kalka Mail train was travelling from Howrah to New Delhi Sunday when at least 12 coaches jumped the tracks near Fatehpur in Uttar Pradesh state.

The cause of the derailment was not immediately clear.

Officials say the number of casualties is likely to rise as rescuers made their way through the twisted coaches.

India's railway network is one of the largest in the world. Accidents are common, with most blamed on poor maintenance and human error.