Clean-up, investigation begin after fuel refinery blaze

With concerns of shortages after a major fuel refinery blaze played down by the company and energy ministers, attention has turned to clean-up efforts and the search for answers.

The fire broke out late on Wednesday at the Viva Energy Geelong refinery, southwest of Melbourne, which supplies more than half of Victoria's fuel and about 10 per cent nationwide.

Prime Minister Anthony Albanese is due to tour the site after flying home early from a trade mission to Malaysia, describing the scenes of the blaze as "very distressing".

With smoke from the fire detectable for many kilometres, concerns were raised over air quality and potential chemical run-off into the nearby Corio Bay.

"When you have a big refinery like that, there's a number of things that are potentially a problem," Oliver Jones, a professor of chemistry at RMIT University, told AAP.

"You've got a load of hydrocarbons, you've got benzene, you've got very small particulate matter that might get off site."

EPA monitoring showed the impact on local air and water quality was minimal, but precautionary warnings were posted for nearby waterways and testing continues.

Energy Minister Chris Bowen said while the disaster was "not good for the atmosphere and the environment", emergency authorities had not flagged any specific health and safety concerns.

University of Melbourne chemicals expert Ian Rae said one of the hazards of any big fire was what happened to the dirty water after it had been sprayed on the fire.

"When there are fires of any sort, particularly where things like petroleum or chemicals are involved, there's a lot of water washed away into the environment," Professor Rae said.

"The first thing they want to do is start putting out the fire, and then they start putting in barriers to stop the fire water getting into the environment."

Prof Rae said such accidents at Australian refineries were extremely unusual, as stringent safety measures were crucial for dealing with such delicate and dangerous chemicals.

"Those places, they're extremely dangerous and they're extremely well run," he said.

"Fires like that are very unusual because they know how dangerous it is.

"There are regular inspections to every little bit of it to make sure it's working, but somehow something got missed this time.

"It's hard to know what happened, but it might have been something simple, like a pipe rupture or a valve that was leaking and nobody noticed for a little while."