At least 17 people have been killed and dozens more hurt after a train derailed in eastern Iran, reports BBC citing state media report.
The train, which was carrying 348 passengers, came off the line between the cities of Mashhad and Yazd about 50km (31 miles) from Tabas.
Emergency services officials said the train collided with an excavator before being knocked off the track.
They warned that the death toll could rise because many of the injured were in a critical condition in hospital.
Tabas County Governor Ali Akbar Rahimi told state media that four of the train's seven carriages were knocked off the line.
Footage posted online by local media showed a number of carriages on their side, as well as a yellow excavator on its side by the track.
National rescue service spokesman Mojtaba Khaled told reporters that a large rescue operation was under way and that three helicopters and 10 ambulances had been dispatched to the scene.
State TV broadcast footage from a hospital where the injured were receiving treatment. One of them told a reporter that they felt the train brake suddenly and then slow before the derailment.
An investigation has been launched by the Tabas prosecutor to establish how the train came to strike the excavator.
One official suggested that the excavator might have been part of a repair project, the Associated Press news agency reported.
Iran saw its deadliest train disaster in 2004, when a train loaded with petrol, fertilizer and cotton crashed near the north-eastern city of Neyshabur, killing almost 320 people.
And in 2016, 49 people were killed when a train that had broken down was hit by another train in the northern province of Semnan.