Flooding spreads to southern AustraliaBy the CNN Wire Staff
NEW:Residents are urged to evacuate Kerang as the levee is compromised
Helicopters are delivering bread, milk and medicine to rural areas in Victoria
Forecasters say more flooding is possible there as rain falls into swollen rivers
At least 20 people have been killed by floods in Queensland state
(CNN) -- Portions of southern Australia kept a close eye Wednesday on rising rivers that threatened to add to the mounting destruction from a month of flooding that has killed at least 21 people, inundated homes and devastated thousands of acres of crops across the country.
Residents of the rural town of Kerang were told to quickly evacuate their homes Wednesday morning as it became clear the levee protecting the town had failed in several places, according to Victoria State Emergency Services.
"You should ensure you have left your property immediately," the agency said in an alert.
The evacuation follows one late Tuesday night for portions of Warracknabeal, an agricultural town of about 2,500 people in western Victoria, about 180 miles northwest of Melbourne.
The agency said overnight flooding there could affect homes by sunrise and leave residents isolated for several days.
Ray Jasper, incident commander for emergency services in Victoria, said helicopters would likely be delivering bread, milk and medicine to remote parts of the state for at least two weeks.
"We have houses inundated. We have a lot of isolated rural properties," he said.
Potential for more major flooding in the state remains strong, CNN International Meteorologist Jennifer Delgado said.
On Tuesday, search and rescue divers found the body of an 8-year-old boy who fell into the water near a river the day before, Victoria police said.
Authorities were still preparing a coroner's report and had not officially linked his death to floods. But earlier Tuesday, Prime Minister Julia Gillard mentioned the boy's disappearance as she briefed reporters on the country's flooding crisis.
"We know many communities are anxiously waiting as floodwaters rise, and many townships across Victoria have already been impacted by floodwaters," she said. "We also know that a small boy is missing, and so these are very difficult times in Victoria."
Gillard said she spoke with victims at a shelter in the state Monday -- many of whom had been evacuated from their homes and did not know what they would find when they return.
"Even in those circumstances, when I met with those Victorians, very many of them said to me that their thoughts are actually with the people of Queensland," she said.
Floods in that northeastern Australian state have killed at least 20 people, police said.
"People have lost their homes, they've lost their workplaces, they've lost their communities and, tragically, a number of Queenslanders have lost their lives," state Premier Anna Bligh told reporters Monday.
In a televised interview four weeks after the state's flood crisis began, Bligh said that an investigation would analyze whether river dams "work as they're supposed to and are operated as well as they technically can be," according to a transcript of the interview published on the government's website.
Police said Monday that 15 evacuation centers housed 1,300 people overnight across Queensland.