One child remains in hospital after eight youngsters fell from a giant inflatable slide at a funfair.
They were injured on Saturday at Surrey's Woking Park where a fireworks display was being held. Seven children have been discharged from hospital.
Donia Echouafni, whose 12-year-old daughter injured her pelvis, told ITV News it was "a traumatic event".
The Health and Safety Executive (HSE) said it was carrying out a "thorough investigation".
Surrey Police has now completed its investigation and has handed it over to the HSE.
The Showmen's Guild, whose members operate equipment at fairs, said the inflatable slide had been taken away by the HSE for testing "in order to establish whether or not there is a design fault or some other cause".
It said it was cooperating fully.
General secretary Joe Mercer said: "As the main trade association for the travelling fairground industry, safety is the number one priority for the Showmen's Guild and it is central to the operation of our members within the industry and we are keen to learn all lessons from any incident however rarely it may occur."
Woking Park was evacuated and a major incident declared after the children - all under the age of 16 - fell at about 19:30 GMT.
None of their injuries were "believed to be significant".
About 5,000 people were estimated to have been in the park at the time.
Ms Echouafni told ITV News how she found her daughter screaming in pain among a "sea" of injured children.
Calling for regulations around temporary fairground rides to be tightened up, she said: "I don't want to see this happen to anybody again, nobody wants to see their child on the floor crying, or unconscious.
"It was a traumatic event for adults let alone children, to see what looked to me to be a sea of children lying down on the ground screaming, unable to move."
Woking MP Jonathan Lord said it was the third such incident of a serious nature in two years, and suggested a temporary ban on inflatables could be a good idea in order for children to be "safe and secure".
Woking District Rotary Club, which helped organise the event, and Woking Borough Council are assisting the HSE in its investigation.
In a statement on Monday, the rotary club said it had been "shocked and distressed", and had started a "full review" of its own.
"We will ensure that any lessons learnt are applied to future events we run," it said.
A spokesman said its thoughts and prayers were with the injured children and their families, and it was relieved to learn that the injuries were less severe than first feared.