A passenger train carrying about 50 travellers derailed as it slowed to enter Northampton station during Monday's evening rush hour.
A Silverlink spokeswoman said no-one was injured in the derailment
The Silverlink 1708 service from Birmingham to Euston was travelling at about 20mph when the front two carriages derailed at about 1810 BST.
A Network Rail spokeswoman said no-one was injured and the area was being treated as the "scene of a crime".
It was believed the train derailed after hitting an object on the line.
The derailment meant the southbound line between Northampton and London was closed, causing some disruption and delay for passengers.