A 39-year-old mother accused of drugging and sexually abusing her eight-year-old daughter at so-called "swinging" group sex parties in Perth has been charged with a further 81 child sex offences against a total of three children.

The new charges, which come on top of 12 initial charges levelled on March 30, include 50 counts of indecent dealing of a child under 13 by a lineal relative and 14 counts of sexual penetration of a child.

She has also been charged with one count of prostituting a child to others.

Police charged three people and arrested three others over the suspected abuse of children. ( Supplied: WA Police )

The children in question include the woman's eight-year-old daughter, her son — whose age was not released by police to protect his identity — and a 14-year-old girl who was unrelated.

Police allege at least some of the abuse took place during organised "swinging" parties staged to allow group sex activities in Perth.

The woman was charged after an investigation was launched in February, after police obtained footage allegedly showing an eight-year-old girl being sexually abused by her mother, stepfather and a male friend of the pair.

Other charges against the woman include stupefying to commit an indictable offence, indecently recording a child and persistent sexual conduct.

Three people have now been charged in connection with the suspected sexual abuse of five young children, and police said last week further arrests and dozens more charges were likely.

Devices being searched

Police are examining a number of hard-drives, laptops, thumb drives and mobile phones that were seized in raids on six properties in Perth and one in the Pilbara region late last month.

A firearm, ammunition, drugs and drug paraphernalia were also seized.

Police said last week they were investigating allegations at least the eight-year-old girl and two other victims were given methylamphetamine or cannabis at the time or just prior to the sexual abuse.

Sorry, this video has expired Perth Police launch major investigation into suspected sexual abuse of young children

Sex Crime Division Superintendent Sharon Leonhardt said the case involved a lot of people over a long period of time and police were seeking public help.

"Specifically, we believe there are people who engage in organised swinging sexual activities who may have heard about or even been unwittingly exposed to activities of these children," she said.

"Consensual sex, group sex between consenting adults is not a crime and this is all about protecting our most vulnerable in the community, so I would say they can give us this information anonymously, they can ring Crime Stoppers."

Police said the children, four girls and one boy, were now all safe and well.

The woman was refused bail and is due to appear in a Perth court soon.