As official donations topped nearly $850,000 on Tuesday, people were warned of fraudsters trying to dupe kind-hearted donors.

A woman told radio station 3AW that she was nearly scammed by someone claiming to be collecting money for the Bourke Street Fund.

The woman, identified only as Mel, said she received a call from a man who said he was from the City of Melbourne and asked for her bank and credit card details.

When Mel questioned the caller, he hung up.

"I said, 'well I'm going to ring up and check'. And he said, 'you can check'. And I said, 'this call is being taped'," Mel said.

"It was a private number."

The official Bourke Street Fund will be available for the families of those who died and people who were injured in the mall attack.

Victims and witnesses will also be able to access compensation from Transport Accident Commission and WorkSafe Victoria.

The TAC can cover the cost of hospital care, rehabilitation, counselling and loss of wages for victims, while WorkSafe can provide similar assistance for people who were at work, or on their lunch break and were affected by the incident.

Scammers also took advantage of kind-hearted community members in the aftermath of the Black Saturday bushfires.

A husband and wife were also charged after taking donated cars and selling them online for their own profit.

Last year, bogus Buddhist monks were scamming people in the CBD and Melbourne's western suburbs by pretending to raise money for Victorian bushfire victims.

Donations for the immediate families of those killed in the Bourke Street tragedy can be made via the website www.vic.gov.au/bourkestreet.html

For urgent support, call Lifeline on 13 11 14. Witnesses and victims requiring support can also call the Victim's Support Helpline on 1800 819 817.