At least 119 people were killed and more than 150 injured when an Indian express train derailed in northern state of Uttar Pradesh on Sunday, with the toll set to rise amid a scramble to locate survivors.
Police officials said people were still missing as authorities tried to ascertain what caused 14 carriages of the train traveling between the northeastern city of Patna and the central city of Indore to suddenly roll off the tracks in Pukhrayan, 65 km south of Kanpur city.
Authorities said they were checking the condition of the tracks but would need to look further before concluding the cause of the derailment, India's deadliest rail tragedy since more than 140 died in a 2010 collision in West Bengal.
Desperate survivors searched for family members and some tried to enter the damaged carriages to rescue relatives and collect belongings, said senior railway official Pratap Rai.
"We are using every tactic to save lives but it's very difficult to cut the metal carriages," he said from the accident site.
Kanpur district magistrate Kaushal Raj Sharma told Reuters that 119 people were confirmed dead, while 78 of the injured remained in hospital, four of them in a critical condition.
With rescue teams still looking for victims amid the wreckage, the toll from the derailment could rise to become India's worst rail tragedy in this century.
In what was probably India's worst rail disaster, a train plunged off a bridge and into a river in 1981 in Bihar state, killing an estimated 500 to 800 people.
India's creaking railway system is the world's fourth largest. It runs 11,000 trains a day, including 7,000 passenger trains carrying more than 20 million people. But it has a poor safety record, with thousands of people dying in accidents every year, including in train derailments and collisions.
Suresh Prabhu, India's railways minister, said in a tweet that the government would investigate the causes of the derailment and promised accountability with the "strictest possible action," as well as compensation for the affected passengers.
The packed train, operated by the government, derailed in the early hours of Sunday when more than 500 passengers were sleeping, survivors said.
TV footage showed mangled blue carriages, with crowds of people and police on top of the wreckage searching for survivors. One carriage was almost lying on its side, and appeared to have been completely torn apart.
Rescue officials with yellow helmets worked their way through the crowds, carrying victims from the wreckage as teams struggled to remove the derailed wagons from the tracks, one of the main transportation routes for goods and passengers in northern India.
"Suddenly I could feel that the carriage was overturning. I immediately held the metal rod near the bathroom door," said Faizal Khan, who was traveling with his wife and two children, all of whom survived the accident.
Another survivor, Rajdeep Tanwar, said. "I can see bodies lying near the tracks, everyone is in a state of shock. There is no water or food for us."
Buses were being pressed into service to help passengers complete their journey, said police additional director general Daljeet Singh Choudhary.
Rescue teams said they would conclude the search operation before night fall and resume it on Monday. Nearby villagers set up temporary kitchens and erected tents for survivors and officials.
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Prime Minister Narendra Modi, who started out selling tea outside a train station, has promised to modernize India's railways and build high-speed lines befitting Asia's third-largest economy.
His government has pledged to replace old tracks and upgrade security infrastructure but little progress has been made so far. More than 90 percent of the railways' revenues are spent on operational costs, leaving next to nothing for modernisation.
By some analyst estimates, the railways need 20 trillion rupees ($293.34 billion) of investment by 2020, and India is turning to partnerships with private companies and seeking loans from other countries to upgrade its network.
Last year, Japan agreed to provide $12 billion in soft loans to build India's first bullet train.
On Sunday, Modi took to Twitter to express his condolences.
"Anguished beyond words on the loss of lives due to the derailing of the Patna-Indore express. My thoughts are with the bereaved families," Modi said.