Witness Laura May said she heard a ‘pop’ from the bus which was ‘like an explosion’.
Ms May, 29, had travelled into the city centre to meet a friend.
“I had just got off the i4, I have come from Beeston to meet a friend,” she said.
“I had just got off the bus, all you could see was smoke billowing from the car park, around the Derbion; it was thick, black smoke – it filled the whole sky. There were loads of people standing around; the security from the Derbion were trying hard to push people back.”
She said the smoke was getting thicker and thicker, adding: “There was a ‘pop sound’ from bus like an explosion.”
Ms May, a key holder who lives in Stapleford, added: “The firefighters are still there dousing in water. It’s a lot clearer than it was.
“All the buses can still get into the bus station.”