(Bloomberg) --

Local authorities are struggling to control a fire at one of Tesla Inc.’s biggest utility-scale batteries in Australia after the blaze initially erupted on Friday.

While the fire has subsided significantly, it is not yet under control, the Victoria Country Fire Authority said in a statement on Monday. The fire occurred within one of the Tesla Megapacks at the Victorian Big Battery during initial testing Friday morning.

“There was one battery pack on fire to start with, but it did spread to a second pack that was very close to it,” said CFA Incident Controller and District 7 Acting Assistant Chief Fire Officer Ian Beswicke. The cause is undetermined and will be investigated once it is safe to do so, according to the CFA.

Battery storage technology is being deployed on an ever-growing scale to meet demand to back up the surge in wind and solar power generation, and Tesla’s technology has been used at several utility-scale projects across Australia.

Australia has been at the forefront of large-scale battery deployment since Tesla Chief Executive Officer Elon Musk in 2017 won a bet on Twitter that he could install one within 100 days. The Victorian Big Battery owned by Paris-based Neoen SA was the latest vying to be crowned the world’s largest.

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