A toxic blaze at the site of Australia's largest Tesla battery project is set to burn throughout the night.
The fire broke out during testing of a Tesla megapack at the Victorian Big Battery site near Geelong.
A 13-tonne lithium battery was engulfed in flames, which then spread to an adjacent battery bank.
More than 150 people from Fire Rescue Victoria and the Country Fire Authority responded to the blaze, which has been contained and will be closely monitored until it burns itself out.
"If we try and cool them down it just prolongs the process," the CFA's Assistant Chief Fire Officer Ian Beswicke said.
"But we could be here anywhere from 8 to 24 hours while we wait for it to burn down."
The Tesla battery is expected to become the largest battery in the southern hemisphere as part of a Victorian Government push to transition to renewable energy.
Ambulance Victoria members are also on site monitoring the health of firefighters.
A toxic smoke warning has been issued near Geelong.
Residents have been warned to close windows, close fireplace flues and bring their pets inside in the Batesford, Bell Post Hill, Lovely Banks and Moorabool areas.
No-one was injured and the site has been evacuated.
Australian Energy Market Operator (AEMO) said the battery had been isolated and disconnected from the main electricity grid and “there are no implications” for supply.
The Tesla battery was paid for by renewable energy company Neoen.
Neoen Australia's Managing Director, Louis de Sambucy said Neoen and Tesla were working closely with emergency services on site to manage the situation.
