An 11-year-old boy is in hospital with potentially life-threatening injuries after the car he was in ended up on a railway line and may have been hit by a freight train.
Northumbria Police said the incident involving a black Land Rover happened close to the A69 between Greenhead and Haltwhistle.
It is understood the rail line runs by the road at this point.
The collision follows the death of four year old Emma Lifsey when a train hit the car she was in at a crossing in Nottinghamshire.
The other person injured in that crash, a 67-year-old woman who was driving, remains in hospital in a stable condition.
A Northumbria Police spokesman said of the latest incident: "The car, for reasons yet to be established, crashed onto the railway line and may have received a blow from a passing train.
"The train stopped further down the line and does not appear to have suffered significant damage and no-one aboard appears to have been injured."
The boy was taken to the Royal Victoria Infirmary by air ambulance.
No-one else from the car appears to have suffered serious injuries following the incident which happened at about 4.25pm.
Three people were treated at the scene for their injuries.
A British Transport Police spokesman said: "The train involved, a Carlisle to Tollerton freight train service, remained upright and on the tracks.
"Officers are working to establish the full circumstances surrounding the incident."
Northumbria Police said it was too early to say whether the sub-zero weather conditions in the area had anything to do with how the car ended up on the railway line.
Earlier on Wednesday the force issued warnings about roads affected by snow and ice.