Two passenger trains in the Indian state of Madhya Pradesh have derailed within minutes of each other, killing at least 20 people, officials say.
The trains were crossing a partially flooded bridge near Harda. Several coaches have fallen into a river below.
A railway spokesman told the BBC that heavy rain had caused river levels to rise, submerging the track.
Officials are saying at least 25 people are injured and 300 people have been rescued.
The Kamayani Express, on its way from Varanasi to Mumbai, derailed first while the Janata Express travelling in the opposite direction derailed shortly after.
The Press Trust of India reported that it was not clear how many passengers the trains had been carrying.
Reports say the trains were crossing a bridge over a rain-swollen Machak river, about 950km (590 miles) from India's capital, Delhi.
"This unfortunate accident took place because of the flash floods on the tracks and the track caved in and resulted in the derailment of the last six coaches of the Kamayani Express," railways spokesperson Anil Saksena told the BBC.
"This train derailed, then simultaneously on the neighbouring line from the opposite direction, another train was coming. That train also encountered a flash flood situation. So it almost happened simultaneously on neighbouring tracks."
Mr Saksena said at least two coaches had been partially submerged in the river, though most passengers had been pulled to safety.
Railways Minister Suresh Prabhu tweeted: "Rushing emergency medical and other relief personnel to spot. Darkness, water creating hurdles but ordered all possible help. Trying our best."
He added that he had ordered an enquiry into the incident.
Prime Minister Narendra Modi has also expressed concern, and offered condolences to the relatives of those who died.
Safety standards on India's massive state-run railway network, which operates 12,000 passenger trains and carries some 23 million passengers every day, has been an ongoing concern amid a spate of accidents.
Last March a passenger train derailed in the northern state of Uttar Pradesh, killing at least 34 people.
And in February last year, at least 11 people died after three coaches of the Bangalore-Ernakulam Intercity Express derailed in the southern state of Karnataka.
Correspondents say the state-run railway network has a patchy safety record - there has been little investment in upgrading decaying tracks and signals and the country lags behind on anti-collision technologies.
Decades of neglect, low investment and subsidised fares have left the network in a shambles.
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