The accident that took place in India's Bihar state and was caused by a rail fracture.
At least eight passengers were killed and more than 20 injured on Sunday after an express train derailed in eastern India's Bihar state, officials said.
Nine coaches of the Delhi-bound Seemanchal Express came off the tracks early Sunday near Sahadai Buzurg station, about 30 kilometres east of the state capital Patna.
"Six people have died and nearly 24 have been injured," Indian Railways spokesman Rajesh Kumar had said before the toll rose to eight.
TRT World spoke to journalist Ishan Russell in New Delhi.
Local television footage showed huge crowds gathered near the accident site as emergency workers cleared the upturned wagons.
Rescue teams with sniffer dogs sifted through the damaged carriages looking for trapped passengers.
Most of the travellers were asleep when the train travelling at 55 kilometres an hour came off the tracks around 4:00 am (2230 GMT Saturday).
"I was sleeping and suddenly there was a big bang and found myself under a pile of bags," passenger Mahesh Kumar told reporters.
A "rail fracture" caused the accident, Indian Railways said in a statement after an initial investigation.
The company promised a thorough probe of the accident, which came days after the Indian government said it had improved rail safety.
Cash compensation of $7,000 would be given to the relatives of those killed, the railways ministry said.
Railways minister Piyush Goyal on Friday had claimed to have improved rail safety after a series of deadly accidents spooked the country.
Goyal told parliament that all unmanned rail crossing had been eliminated, one of the main causes of train collisions in India.
India's railway network is the main form of long-distance transport, but has been lagging in improving its infrastructure, often leading to disasters.
Nearly 150 people were killed after a passenger train derailed in Bihar in 2016, the deadliest accident in recent years.