Tesla Megapack Fire in Australia Blamed on Undetected Coolant Leak

Warning signs adorn the fence surrounding the compound housing the Hornsdale Power Reserve, featuring the world's largest lithium ion battery made by Tesla, during the official launch near the South Australian town of Jamestown, in Australia, Dec. 1, 2017. David Gray/Reuters

MELBOURNE—A fire that damaged two Tesla Inc battery units at a huge energy storage project in Australia in July was caused by a coolant leak that went undetected during start-up tests, a state watchdog said in a report released on Tuesday.

Safety regulators on Tuesday cleared the so-called Victoria Big Battery project, run by French renewables firm Neoen SA, to resume testing at the site near Melbourne.