Of those injured, 11 are reported to be in a serious condition.
The two trains, both travelling towards London, collided at approximately 5:15pm yesterday. Early reports suggest that an East Midlands Railway service struck the rear of another train.
Investigators from the Rail Accident Investigation Branch (RAIB) have said it is too soon to determine the exact cause of the crash. The ongoing investigation will examine CCTV footage, witness accounts, and data from the trains' onboard recorders, which function in a similar way to the black boxes used on aircraft, to establish what led to the incident.
Transport Secretary Heidi Alexander said: "We will ensure a full and thorough investigation is carried out to understand how this collision occurred and to make certain that lessons are learned to help prevent a similar incident from happening again."
People who witnessed the crash described the impact as being comparable to an explosion, with "shrieks and groans of pain" heard in the aftermath.
Passenger Brett Byatt, who was travelling on one of the trains, estimated that around 90% of the people in his carriage suffered injuries, with many reportedly "bleeding profusely".
Other witnesses described those around them as being severely injured and "smashed up" by the force of the collision.
A spokesperson for King Charles said: "His Majesty is greatly saddened by the rail crash in Bedford yesterday evening and is being kept regularly updated on developments. His thoughts and sympathies are with the family of the deceased and with all those injured or affected by such a tragic incident."
