The two trains involved were the 16:40 EMR train from Corby and the 15:50 Nottingham to London St Pancras service.
Dr Peter Knapp, who was travelling in the front carriage of the train that went into the other, said: “When I got up, I saw all of the chairs everywhere. It felt like I’d been in a bomb explosion.
“When I got up, I saw people’s bloodied faces and people’s legs looked broken and there was smoke everywhere.”
Shola Mene said she heard a “big bang” and “people flew from their seats”.
“There was a lot of blood. A lot of people had facial injuries,” she added.
Teresa Itabor, from Wellingborough in Northamptonshire, said she had been heading to the capital to celebrate her birthday.
“We left Bedford station and there was a massive bang… I didn’t know what was going on. My head hit the seat in front of me,” she said.
“I opened my eyes and that’s when I saw people on the floor with blood everywhere.”
Brett Byatt from Bedford told BBC Radio 4’s Today programme he was among three or four people in his carriage who were not injured, adding: “Everyone else had either a serious wound that was bleeding profusely, or a situation where they couldn’t stand, or couldn’t move their neck.”