Det Insp Lucy Forde, from Avon and Somerset Police, said officers spent “hundreds of hours” watching CCTV footage from the nursery’s 18 cameras to isolate Bennett’s offending period and the children affected.
But, according to the force, the footage only spanned back a month before it was overwritten.
Forde described the footage as “absolutely sickening”.
“It is him offending against children in the middle of the nursery in sight of other children.
“There is nothing that could prepare you for seeing that,” she added.
A total of four victims were identified through CCTV, and a fifth came forward after confiding in their parents what had happened.
“My worry if there will be other victims that we haven’t been able to identify, that are too young to understand what’s happened to them,” Forde said.
The force has now opened a public portal for parents with children that attended the nursery can log any concerns, external and speak to specially trained officers from its child protection team.