Eleven people were treated in hospital after a stray firework landed in a crowd gathered to watch a bonfire night event at Wicksteed Park in Northampton.
Most of the injured were children and it is understood that a 10-year-old boy received the most serious injuries, requiring surgery for burns to his legs.
The firework display, which attracted around 15,000 visitors to the park on 5 November, was organised by Kimbolton Fireworks.
John Roberts, Wicksteed Park’s managing director, said: “We host a number of large events and had gone through a very thorough process of planning with the local authority and emergency services.”