At least eight people were killed in India on Monday when a goods train driver missed a signal and slammed into an express passenger train from behind, police and railway officials said.
Three passenger carriages were derailed and flipped on their side, while one carriage was thrust high into the air, precariously balanced on another.
The incident in West Bengal state is the latest to hit India's creaking rail network, which carries millions of passengers each day -- and the most recent reported failure of drivers missing basic signals.
Around 50 people were injured and taken to hospital, Jaya Varma Sinha, chairman of India's Railway Board said in a statement.
"A goods train disregarded the signal and hit the train from behind," Sinha said.
The dead included the driver and co-driver, who missed the signal, as well as a train guard and five passengers, she added.
Sinha said the casualties could have been worse, but a guard wagon and two others carrying post that were attached to the back of the passenger train took the brunt of the crash.
"There were two parcel carriages attached... which protected other carriages from extensive damage," she said, but added that the guard wagon "was badly damaged".
- 'Tragic' -
The crash took place in the Phansidewa area of Darjeeling district, when the Kanchenjunga Express train was hit by the goods train.
Prime Minister Narendra Modi offered his condolences to "those who lost their loved ones", in a post on social media.
West Bengal's Chief Minister Mamata Banerjee called the crash "tragic".
Moments after the collision, she said that "ambulances and disaster teams" were rushed to the site, giving orders for "action on war footing" to be initiated.
Local police officer Iftikar-Ul-Hassan told AFP he saw several badly injured people pulled out of the wreckage.
"The toll could rise further, as four people are admitted in a serious condition," he said, adding that rescue teams were working to return the line to service.
"The tracks are being cleared and restored for operations", he added.
- World's highest rail bridge -
India has one of the world's largest rail networks and has seen several disasters over the years, the worst in 1981 when a train derailed while crossing a bridge in Bihar state, killing an estimated 800 people.
In June last year, a three-train collision killed nearly 300 people in Odisha state.
In that crash, a packed passenger train was mistakenly diverted onto a loop line and slammed into a stationary goods train loaded with iron ore.
Three railway employees were later charged with culpable homicide and destruction of evidence.
In October, at least 14 people died when two passenger trains collided after one overshot a signal in Andhra Pradesh state.
The railways ministry said that drivers had been distracted because they were watching cricket on a phone, as hosts India played England during the one-day World Cup.
In March, Minister of Railways Ashwini Vaishnaw said the train board was "installing systems which can detect any such distraction" to make sure drivers were "fully focused on running the train".
In recent years, India has been investing huge sums of money to upgrade its network with modern stations and electronic signalling systems.
On Sunday, a train crossed for the first time the world's highest railway bridge -- 359 metres (1178 feet) above a river -- in India's Himalayan region, Vaishnaw said.
The arch-shaped steel structure over the Chenab River links sections of northern Jammu and Kashmir state, connecting the disputed territory to the rest of India.
Work on the railway track has been ongoing for nearly three decades, and the trial run comes ahead of a formal opening expected within weeks.