At least three people have been killed and up to 40 injured after a Pakistani train plunged down an embankment, officials have said.
The incident occurred as the train, travelling to Lahore from Rawalpindi, neared Jhelum city in eastern Punjab.
The mountainous area was inaccessible by road, and troops had to use another train to access the site.
Rescuers worked in darkness to pull out survivors from the train, which is the fastest in service in Pakistan.
One passenger quoted by the Associated Press said he was riding in the first carriage when he heard a big bang and felt a huge jolt.
"I heard screams," Javed Butt said.
Some of the compartments were so badly damaged that rescuers had to use metal cutters to free survivors.
The cause of the the derailment is unknown but railway authorities said an investigation would begin on Monday.
Hundreds of people have died in recent years on Pakistan's railways.
More than 130 people were killed near the southern town of Ghotki last July, in Pakistan's worst train disaster in at least a decade.
Correspondents say casualty figures are often so high because trains are packed with far greater numbers than they were designed for and that signalling faults or poorly maintained tracks are often the cause.
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