A freight train has derailed west of Geelong, leaving dozens of shipping containers strewn across railway tracks.
Sixteen wagons came off tracks between Inverleigh and Gheringhap about 5:30am.
The SES said nobody was hurt in the incident and there were no dangerous goods onboard.
The derailment happened close to a level crossing, which was temporarily closed, but has now reopened.
SES chief operations officer Tim Wiebusch said there had been substantial damage to the tracks, but it would take some time to determine the cause.
"We know there was heavy rainfall and some flash flooding in that area but at this stage it's too early to know what the cause was of the train derailment," he said.
Mr Wiebusch said it was extremely fortunate the accident wasn't more serious.
"We were incredibly lucky we weren't dealing with a passenger train in this instance and that the crews on board that freight train also came out of that event unscathed," he said.
"They are assessing how to get heavy machinery there to remove the wreckage but also reinstate the line so it could be a week or more before we start to see active work on that line."
Victoria was hit by wild weather overnight, resulting in widespread flash flooding.
Inverleigh resident Robyn said there was torrential rain in the area overnight.
"There's at least 20 containers just everywhere and Inverleigh itself is pretty much awash with just water over the roads everywhere," she told ABC Radio Melbourne.
"The Leigh and Barwon [rivers] meet together in Inverleigh and it's just a lake.
The Australian Rail Track Corporation (ARTC) said it was working with freight customers on a recovery plan.
The Office of the National Rail Safety Regulator has been notified and the Australian Transport Safety Bureau has taken control of the site.
The ARTC said it would provide further details and an update on when the interstate freight corridor would re-open once a full assessment of the area was completed.
The Australian Transport Safety Bureau's (ATSB) chief commissioner Angus Mitchell said a team of safety investigators had been sent to the site.
"Investigators will survey the site and collect any relevant components for further examination and analysis," Mr Mitchell said.
"They will also obtain and review any recorded data, weather information, witness reports, and relevant train and track operator records."
A report will be published at the conclusion of the investigation.
"However, should any critical safety issues be identified at any stage during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate safety action can be taken," Mr Mitchell said.
Fears of freight delays
The Melbourne to Adelaide rail corridor is closed while the wreckage is cleared and the damage is assessed and repaired.
"You don't go through such a significant event such as we have seen in Victoria, New South Wales, without some impacts in relation to movement of freight, of goods, of people," Emergency Management Commissioner Andrew Crisp said.
"But so many people [are] doing such an incredible job to make sure we are opening up roads, opening up rail and other ways of moving freight as quickly as we can."
The freight industry said the incident would cause further disruptions to road and rail supply chains that were already facing challenges from recent flooding in Victoria.
The Victorian Transport Association CEO Peter Anderson said it added weight to his recent call for federal and state funding for a coordinated plan to tackle the massive job of repairing and reinstating road and rail freight networks.
"We need our political leaders out there committing resources to fix the damage that's been done as soon as possible in what are clearly unprecedented rain and weather events," Mr Anderson said.
He said the closure would result in an increase in road freight transport between Melbourne and Adelaide.
"Freight will always find a way to get to customers and consumers, particularly during our peak season leading into Christmas," he said.
"With the expected increase in heavy vehicle traffic we ask all motorists to take additional care on the roads to prevent accidents and keep everyone as safe as possible."
