Police searching a lake behind the home of missing Gold Coast woman Wendy Sleeman have recovered a knife and a CCTV system from the water.
Earlier on Wednesday, police said they held grave concerns for Ms Sleeman after officers discovered fire damage and a large amount of blood at her home.
A crime scene has been established and detectives have issued an urgent plea for public assistance in finding the 61-year-old and her 30-year-old son, Slade Murdok.
Regional Crime Coordinator Detective Superintendent Brendan Smith said officers were called to Ironbark Street at Elanora just after 3.30pm on Tuesday after reports of a burglary and a fire.
He said emergency services arrived within 30 minutes to find blood at the property and a doormat on fire, but that Ms Sleeman could not be located.
On Wednesday afternoon, police divers began searching a lake behind Ms Sleeman's house, recovering a knife and parts of a CCTV recording system.
"I can say I have grave concerns," Superintendent Smith said.
He added that there were "clear signs of violence" at the scene, and that Ms Sleeman's disappearance was out of character.
Police sources told the ABC Ms Sleeman had phoned triple-0 earlier on Tuesday after Mr Murdok allegedly arrived at her Gold Coast workplace wearing a mask.
It's understood she told police that when she returned home later that day there was a broken window at her Elanora property and the hard drive connected to her CCTV system had been stolen, along with a laptop.
Neighbours who know Ms Sleeman said they are struggling to come to terms with her disappearance.
They told the ABC that Mr Murdok had a "fixation" on his mother, and his behaviour had been escalating.
The neighbours, who did not want to be identified, said police were called to Ms Sleeman's home last week after her son triggered an alarm at the property.
Superintendent Smith said nobody had been able to make contact with Ms Sleeman since Tuesday afternoon.
"It's very important that police receive community assistance," he said.
Ms Sleeman is described as Caucasian, approximately 153cm tall with a heavy build and short brown hair.
Her son, Mr Murdok, is described as Caucasian, 180cm tall with brown hair and a slim build.
He is believed to be travelling in a blue Honda Jazz with registration 952AT4.
Superintendent Smith said police were also aware of a white Ford Laser sedan seen in nearby streets at the time of the disappearance, the blue Honda Jazz was of the most interest to police.
"We believe the son was using that car to get around, he was in Surfers Paradise earlier in the day," he said.
"The blue Jazz is of the greatest interest because we have information that (it) left around the time the woman went missing."
Police are investigating claims that Mr Murdok was seen taking a taxi to Brisbane's south side.
Members of the public have been urged not to approach Mr Murdok if they see him, and to instead call triple-0 immediately.
