A fourth person arrested was released due to insufficient evidence
Police charged a fourth person they suspected was part of a paedophile ring at a Plymouth nursery but the case was later abandoned, it has emerged.
Vanessa George pleaded guilty, along with Angela Allen and Colin Blanchard, to a string of child sex offences in a case described by police as "devilish".
A woman from Liverpool was charged with abuse offences but the case was dropped in July due to insufficient evidence.
George has not disclosed which children were abused.
Dozens of parents still do not know whether their children were among those abused.
The judge urged George, 39, who met the others online, to do the "decent thing" and name children she had assaulted.
George, who worked at Little Ted's nursery in Plymouth, admitted a string of chilling sexual assault offences involving children as young as 12 months.
She swapped pictures of the abuse with Blanchard and Allen, both also 39, who admitted similar charges at Bristol Crown Court.
The fourth person arrested had been charged with assaulting a child under 13, as well as making and distributing indecent images, before the case was dropped.
George, Allen and Blanchard, all 39, met via the social networking site Facebook. They had never met in person before appearing at Bristol Crown Court on Thursday. They are due to be sentenced next month.