A man has died following a low-speed collision involving two trains in Wales, British Transport Police (BTP) has confirmed.
A further 15 people have been taken to hospital with injuries not believed to be life-threatening or life-changing, the force said.
All other passengers have been moved away from both trains, one of which was travelling from Shrewsbury to Aberystwyth and the other from Machynlleth to Shrewsbury.
The crash happened near the village of Llanbrynmair, in Powys, at about 19:30 BST on Monday.
Anthony Hurford, a passenger on the Shrewsbury-bound train, said he felt "pretty shellshocked" by the incident.
"Somehow my body bent the leg of a table and ripped it off its bolts attached to the wall.
"Suddenly I was on the floor with my laptop strewn ahead of me, wondering what the hell had happened," he told BBC Breakfast.
Ifan Edwards, a witness who lives near the scene of the crash, said he saw a number of ambulances passing, an air ambulance and two Coast Guard helicopters.
He said it appeared that one of the trains had failed to stop in the normal place on a hill "and from what we can gather he just slid and he couldn't stop the train".
The Cambrian railway east of Machynlleth will be closed while investigations continue, Network Rail and Transport for Wales said, urging passengers not to travel on that part of the network.
"We're extremely grateful to the emergency services who attended the scene and helped our passengers and staff in challenging circumstances."
The services involved were the 18:31 from Shrewsbury to Aberystwyth and the 19:09 from Machynlleth to Shrewsbury.
Police have closed the road, less than a mile from where the collision took place.
The A470, the main road from north to south Wales, runs adjacent to the line and the emergency services are working from it at a point which is quite close to the site of the collision.
The train, as we understand it, is still upright on the track, according to one of the passengers who came out after the collision.
Traffic Wales said the A470 was closed in both directions between Caersws and Glantwymyn, while Transport for Wales said rail replacement services were in operation.
The incident was attended by the ambulance and fire services, local police, and the coastguard, with support from the rail industry, BTP said in a statement.
Residents reported seeing an air ambulance at the scene.
BTP said the family of the man who died had been informed and was being supported by specialist officers.
It also said local residents would see an increased police presence in the coming days as officers worked to understand the circumstances leading up to the collision.
Writing on X earlier, Welsh First Minister Eluned Morgan said: "My thoughts are with all those involved in the rail incident in Powys earlier this evening.
"I would like to thank the emergency services for their response and have asked to be kept informed of any developments throughout the night."