Deliberate steps were taken to 'fool people' into believing a mother decomposing in a bathtub for eight months was alive and well, police said.

The body of 40-year-old Sarah Gatt was discovered in a Kensington unit on January 3 this year, but police believe she died between April 20 and 24 last year.

Forensic evidence indicates a violent assault took place and investigators believe efforts were made to conceal the mother of four's fate and fool people into thinking she was still alive.

An undated photo of Sarah Gatt. (Supplied) (Nine)

Police believe someone was living at the home on-and-off while the body was being concealed in the bathtub.

Officers discovered the body after attending on an unrelated matter. They detected a smell and subsequently entered the property, where they located Ms Gatt.

Ms Gatt's body was so badly decomposed that bone needed tested to help identify her.

The mail at the address was overflowing and lawn overgrown. (9NEWS) (Nine)

Ms Gatt's body is removed from the home. (9NEWS) (Nine)

Three men and two women were questioned in January about the death but weren't charged and remain persons of interest.

"It's disturbing and concerning to investigators that it appears someone has deliberately attempted to make it look as though Sarah was still alive," Homicide Squad Detective Inspector Tim Day said.

"There are people out there who know what happened to Sarah and we are urging them to come forward and speak to police."

Her father Victor Gatt told reporters he lost contact with Sarah about 18 months ago.

Victoria Police today released the first image of Sarah Gatt, who was found dead in her bathtub. It is unclear when the photo was taken. (Victoria Police) (Nine)

"She didn't want to see me anymore," he said.

"Whatever I said, she just didn't want to do it."

Ms Gatt attended modelling school as a teenager and began using drugs, her dad said.

Ms Gatt's emotional mother breaks down pleading for information. (9NEWS) (Nine)

"I put her in different places to try and get her cleaned up but it didn't happen."

Mr Gatt described his daughter as a "tomboy" and a "great person".

"I couldn't fault her at all," he said.

Bags of evidence were loaded into a police van. (9NEWS) (Nine)