17/08/2017 4:10 PM AEST | Updated 17/08/2017 4:11 PM AEST

Man Kills Himself Hours After Police Announce Wife's Murder Investigation

'It is very, very unlikely that she is alive.'

Tanja Ebert, 23, has been missing since last Tuesday. Her husband Michael Burdon, 41, took his own life after police interrogated him over her suspected murder.

The husband of a missing 23-year-old woman has taken his own life on the family's sheep farm in South Australia, hours after police announced they were treating her disappearance as murder.

Tanja Ebert hasn't been seen since last Tuesday, August 8, and police say it's "very, very unlikely" that she is still alive.

At 2:30pm on Wednesday August 16, police held a press conference to say they were treating Ebert's disappearance as a murder inquiry.

By 5pm that afternoon, her husband Michael Burden was dead. He slipped away from investigators as they scoured the family property near Manna Hill for evidence and fatally shot himself.

Major Crime officer-in-charge Detective Superintendent Des Bray told reporters on Thursday morning that Burden was a "suspect" in the murder, but he was not under arrest at the time and had made no admission of guilt.

Tanja and Michael were married in February, but police say cracks were already appearing in their relationship.

"At this point in time there is no evidence to prove that Michael is responsible for the murder," he said.

Forensics teams continue to search the vast sheep property, close to the NSW border, where the newlyweds lived with their two young boys, aged one and three.

Friends described the couple -- who were wed in February -- as "a match made in heaven", but Detective Superintendent Bray said police had received reports of "issues within the relationship" and they believed Ebert "was intending to leave the family home".

Burden had earlier told police that the last time he had seen his wife was driving home from a trip to Adelaide on August 8. She had allegedly become distressed and refused to return to the family property, getting out of the car near Roseworthy, 56 kilometres north of Adelaide, and taking a large sum of money.

Tanja Ebert, 23, with her two young sons. The children have been placed in the care of relatives.

A wide-scale search of that area was conducted but police say it has now been eliminated from their inquiries.

The last confirmed sighting of the German national -- who came to Australia for a gap year in 2011, where she met Burden -- was at 3:20pm last Tuesday, when a CCTV camera captured her leaving the South Australian Museum in Adelaide.

She was reported missing two days later by a relative in Germany after the family had been unable to reach her.

The couple's two young children are being cared for by family members.

Detective Superintendent Bray said police would conduct a "very intense" search of the family's 420 square kilometre property, but it was a "massive task".

A commissioner's inquiry has begun into Burden's death, which will be conducted independently of Tanja Ebert's murder investigation.