Victoria's transport union says train drivers from the state's regional rail service had been refusing for the past week to traverse a section of track where a Sydney-to-Melbourne train derailed last night, killing two people.
The XPT train, which was carrying 153 passengers, was travelling from Sydney to Melbourne when it derailed at Wallan shortly before 8:00pm.
The train's driver, a 54-year-old ACT man, and train pilot, a 49-year-old Castlemaine woman who worked for Skilled Rail Services, were killed.
The Rail, Tram and Bus Union (RTBU) said it was "deeply saddened by the tragic accident that has taken the life of two rail workers and unnecessarily injured many more".
"The Sydney to Melbourne XPT train derailment near Wallan Station last night occurred over a section of track over which was awaiting maintenance," RTBU state secretary Luba Grigorovitch said in a statement.
"Conditions were altered and V/Line drivers rightly refused to traverse this section over the past week."
The president of the Rail Futures Institute, John Hearsch, told AM a fire at a signalling facility close to the accident site had recently affected signalling between Donnybrook and Kilmore East.
"So I'm sure the ATSB [Australian Transport Safety Bureau] will be looking very closely at that to see whether there's a link between the signalling problems, the set of points at the entrance to the crossing loop and the accident," Mr Hearsch said.
Passenger Leyon Gray said the train derailed just minutes after taking off again after sitting stationary on the tracks.
"They [staff] said we could be there for half an hour because the signals were malfunctioning," he said.
"And the train got going and we were probably doing 80 or 90 [kilometres] an hour.
"Next thing we were thrown out of our seats."
V/Line had reported several delays between Albury and Southern Cross stations in recent days due to an "ongoing track fault".
Shortly after 4:00pm yesterday, the Seymour V/Line Twitter account said the 12:45 Albury to Southern Cross service would be delayed by approximately 70 minutes due to an "ongoing rail equipment fault near Wallan".
'Too early to speculate' on cause
National Rail Safety Regulator chief executive Sue McCarrey told ABC Radio Melbourne that works underway on the line would be among a range of factors examined by investigators.
Key to the investigation would be the speed limit on the track at the time and the speed of the train, which would have been recorded by the train's data log.
"It's very early days to speculate on what the causes actually are," Ms McCarrey said.
She said two rolling stock experts and a signalling engineer were among the team of investigators already out on site.
Ms McCarrey said she was aware of media reports that the driver told passengers over the public address system ahead of the crash that he was going to try to "make up time".
"Again, that's something else to look at as part of the investigation," she said.
"We will be interviewing a number of people to try and determine what the actual facts are what was said over the PA at the time."
However, she added that drivers could not exceed speed limits set by the safety management system which varied due to factors including the condition of the line and weather conditions.