British Transport Police said on Friday that it was responding to reports of a collision between two trains in the city of Bedford in eastern England, as emergency crews headed to the scene and authorities worked to assess the situation.
Bedfordshire Fire and Rescue Service said its teams were at the site of the incident on the railway line just south of Bedford, and urged people to avoid the area.
Thameslink said all lines between Luton and Bedford were suspended due to a problem that was being investigated.