A mother and her bother, who were brutally stabbed to death in full view of the mum's 4-year-old daughter, were targeted by accident, police have confirmed.

April and Ian Bailey were found dead inside their fire-ravaged home at Deception Bay, north of Brisbane, Australia, on May 28, 2004.

Last week, 34-year-old Danielle Lee Fels was arrested over the incident as police made a fresh appeal for information, suspecting up to four people were involved in the crime.

Detective Inspector Damien Hansen confirmed the siblings, who were allegedly killed in front of April's daughter Violet, were targeted because of the actions of another woman called April from the same area. "April had come into possession of a large quantity of drugs," he told The Courier-Mail.

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"But it was not April Bailey - they've got the wrong April.

"It's not even the wrong place at the wrong time. They were targeted through just an unfortunate set of circumstances."

The Courier Mail reported that several calls were made to triple zero soon after the house fire.

The first was believed to have captured Ian screaming while Violet is believed to have made the second call, in which people could be heard ­arguing.

Queensland Police this week urged a mystery caller with vital information to phone investigators back.

The anonymous caller was among more than 15 people who phoned police after seeing media coverage of Fels' arrest.

Violet, now 17, has urged anyone with information to come forward and an offer of a $250,000 reward and indemnity from prosecution still stands. Fels appeared in court on Monday morning and was remanded in custody until December 20.