Police close in on violent Vic killer

Almost three years after her violent murder, police are confident they are closing in on the killer of Melbourne mum Kylie Blackwood.

The 42-year-old was found bleeding to death by her 11-year-old twin daughters in their home in Pakenham when they returned from school on August 1, 2013.

It seemed to be a burglary gone wrong.

Now investigators are pinning their hopes on a significant breakthrough coming from new CCTV footage released on Thursday of a white Nissan Tiida seen in the area before and after Ms Blackwood's death.

Detective Inspector Mick Hughes says there are a number of persons of interest - but he refused to single out any one suspect.

Instead he issued a warning to Ms Blackwood's killer.

"We know we will get to you," he said on Thursday.

The detective says being able to link that car to a man seen acting suspiciously in the area on the same day could help solve the crime.

Police have received more than 200 calls about the murder since Ms Blackwood's death and are urging anyone who can help further to make contact again.

"Somebody out there knows this person, knows the car and is able to link them ... you may help us solve this," Det Insp Hughes said.

Police have already zeroed in on 30 of those cars registered in the Pakenham area in 2013 and will focus there first.

They will widening their scope to all of the 900 cars across the state if needed, he said.

It's believed attempts to withdraw money from Ms Blackwood's bankcard were made at the local bank on the same day, but footage of the ATM was lost before detectives learned of its existence.

Ms Blackwood, a popular figure in the semi-rural town, left behind her daughters, a 13-year-old son and her husband Peter.