Police forensic experts are working to discover how Brisbane woman Allison Baden-Clay died.

The worst fears of Ms Baden-Clay's family were realised on Tuesday when police confirmed a woman's body found on a creek bank was that of the 43-year-old mother, who is believed to have been murdered.

"The heavy rain that we've had over a period of time ... may indicate that the body may have washed down ..." to the place it was found," Detective-Superintendent Mark Ainsworth told reporters on Tuesday.

The lawyer for Mrs Baden-Clay's husband Gerard said his client was devastated.

"His primary concern is the welfare of his three very young daughters and attempting to provide some stability and normality to them," Darren Mahony said in a statement on Tuesday.

The corpse was spotted by a canoeist on a creek bank in the suburb of Anstead on Monday, about 10km west of the Baden-Clay's home suburb of Brookfield.

It was found about 300m downstream from a scout group's campsite.

Police will not say whether they have a suspect in the case.

"A number of people have been interviewed, a number of people have been interviewed more than once, but I can confirm that we're looking at an unlawful homicide investigation," Det Supt Ainsworth said.

A search of the area where Mrs Baden-Clay's body was found has turned up a mobile phone SIM card, a pair of gloves and general items of rubbish.

Police say the items will undergo testing and they will continue to search the area for clues.

Mr Baden-Clay reported his wife missing from their home on April 20, reportedly after she went for a late-night walk.