Sources told Fairfax Media that John Torney, who was charged last week with the murder of the two-year-old, was a regular user of the drug.

Mr Torney, 31, the boyfriend of Nikki's mother Peta-Ann Francis, was charged on Friday after the toddler's body was found in the roof cavity of the Oram Court home about two hours after her mother reported her missing last Tuesday afternoon.

A young policeman made the grim discovery when he decided to check the roof after police had already searched through the home.

Nikki reportedly suffered blunt-force trauma.

In other developments, the family of Mr Torney have told police of receiving death threats since the arrest.

Mr Torney, from south-east Queensland, had been living in the home with Ms Francis and her four girls, all aged under eight.

He moved from Ipswich with his then-girlfriend in late December, and lived with his mother, whose house was across the street from Ms Francis.

When he separated from his girlfriend, he had a brief relationship with another woman before he started seeing Ms Francis in late February.

He moved in within weeks, and had been living there permanently.

Sources close to the investigation say Mr Torney has battled drug addiction and was using ice but it was unclear when he had last used.

A person who knew Mr Torney said drug use was not his only issue.

"Johnny had all the issues: drugs, gambling, smoking and drinking."

Ms Francis is also believed to have been a regular user of cannabis, and had used ice.

Detectives have established that Ms Francis claims she left Nikki alone with Mr Torney on at least two occasions last Tuesday, but it remains unclear when Nikki was last seen alive.

Ms Francis said she had put Nikki to bed about midday - earlier than usual - and checked her again about 1pm. She was reported missing about 3.15pm.

Neither Ms Francis or Mr Torney was employed, and the children relied heavily on the assistance of their extended families, and the relatives of Mr Torney, along with local support services.

Mr Torney, one of six children, has several siblings in the Mildura region. He is a father of two, but has not seen his children, who are based in Queensland, for several years.

It is not believed he had been violent towards his own children, and the person who knew Mr Torney said he had a good relationship with Ms Francis' children, especially Nikki.

Nicholas Coslovich, the father of Nikki and her three sisters, had not seen his daughters for several weeks.

Ice, along with family violence, has driven a substantial amount of crime in Mildura with police estimating that ice accounted for 90 per cent of all drug-related arrests in 2013-14.

The prevalence of the drug led to the creation of one of the first community-based campaigns in the state, dubbed Project Ice, and Mildura was the only Victorian town to be included in the national ice taskforce consultations.