At least 31 people have been killed and 100 others were injured after a packed express train derailed in northern India.

Rescuers are searching the wreckage of the Kalka Mail train for survivors after it derailed on its way to Kalka, in the foothills of the Himalayas, from Howrah, a station near Kolkata in eastern India.

Twelve coaches and the engine left the tracks at Malwan station, near the town of Fatehpur in Uttar Pradesh state, a senior railway official said.

The cause of the derailment was not immediately clear but it appeared that the driver applied the emergency brakes, the official said.

At least 31 people were killed and rescue workers pulled at least 100 injured passengers out of the wreckage, according to state police.

The accident site was a pile of twisted metal. At least one coach was left dangling precariously after it flew above the roof of another just ahead of it, television footage showed. Another coach was thrown away from the rest of the train.

The death toll is likely to rise as rescuers make their way through the coaches and use gas cutters to get through the mangled metal, Lal said.