Network Rail has warned that disruption between London and Bedford is expected to continue for a week following a fatal train crash, which it described as a "tragic, isolated incident".
A train driver was killed and about 100 people were injured when two East Midlands Railway (EMR) services to London St Pancras collided at about 17:15 BST on Friday near Bedford.
Police said 28 people remained in hospital, including nine in a critical condition.
EMR services to and from London St Pancras have been suspended over the weekend, while Thameslink has urged passengers to travel only if essential.
Network Rail said the line is expected to remain closed between Bedford and Luton for the rest of the week, until 28 June.