By Agence France-Presse
"I just heard this massive bang and then everyone just started running towards us screaming and crying. Everyone just trampled over us just to get out," Jessica, a concert-goer, told BBC radio.
Jessica was among the 21,000 people who had just watched the American pop sensation, who is particularly popular among teenagers, perform in the northern English city when there was a "huge bang".
"Everybody was panicking," Isabel Hodgins, an actress who had been attending the concert told Sky News.
"The corridor was full, it smelled of burning, there was quite a lot of smoke as we were leaving".
Elena Semino, who was waiting for her 17-year-old daughter and was herself injured, told the Guardian newspaper: "There was heat on my neck and when I looked up there were bodies everywhere".
Semino said she had been standing by the arena's ticket office when the explosion went off.
Cheryl McDonald, who went with her nine-year-old daughter, told Sky: "I've never been so scared in my life. My daughter is very, very shocked".
McDonald broke down as she described a "devastating" scene, saying the venue was "full of children".
Gary Walker, who had been waiting for his daughters and got hit by shrapnel to his leg, said he was "metres away from an explosion".
"Someone came through the doors then bang," Walker, whose wife sustained a stomach wound, told BBC radio.
His daughter Abigail said: "I had to make sure I had my sister. I grabbed hold of her and pulled hard. Everyone was running and crying.
"It was absolutely terrifying," she said.
Emergency services said they had taken 59 casualties to various hospitals as well as treating a number of walking wounded at the scene.
Emma Johnson, who told BBC radio she and her husband were at the arena to pick up their 17-year-old son and 15-year-old daughter, said the explosion was "definitely" in the foyer.
"We were stood at the top of the stairs and the glass exploded. It was near to where they were selling the merchandise. The whole building shook.
"There was a blast and then a flash of fire afterwards. We obviously then run to try and find our children and fortunately for us we were all safe to tell the story."