Western Australian Police have launched a major investigation into the suspected sexual abuse of at least five young children during organised sex activities with groups of adults.

The investigation was launched last month 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.

The trio, aged between 39 and 56-years-old, have been charged with a total of 23 offences, including sexual penetration and indecent dealings with a child.

Officers searched six properties in Perth and one in the Pilbara on Thursday and three more people were arrested in connection with what police have described as alleged organised group sex activities, or swinging.

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

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

A search warrant was executed at a home in South Australia on Monday.

Plea for public's assistance

Further arrests and dozens more charges are expected to be laid, as police examine a number of hard-drives, laptops, thumb drives and mobile phones.

Police are further 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.

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

Sex Crime Division Superintendent Sharon Leonhardt said the initial video was handed to authorities after being found on a device at a rental home in Perth's western suburbs.

"We were lucky that this was handed in because, initially, we thought it was a bit of a one-off and it obviously has become a far more serious investigation," Superintendent Leonhardt said.

She said the case involved a lot of people over a long period of time.

"I fully expect that there will be further arrests and many more charges proffered, but the taskforce needs the assistance of the community to identify all the persons that have been offending against these children," Superintendent Leonhardt said.

Police expect there will be further arrests. ( Supplied: WA Police )

"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."

Superintendent Leonhardt said she understood some people may be embarrassed to admit involvement in swinging activity, but stressed the need to share any information with police.

"This is a very serious offence, no one, absolutely no one in our community should be turning a blind eye when they know that children are being sexually assaulted, and particularly when parents are involved," Superintendent Leonhardt 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.

All three accused will face court next month.