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. However the safety regulator Energy Safe Victoria said it will now determine whether there have been any breaches of the state’s electricity safety rules and “if so, whether enforcement action is warranted.” Neoen said it is working with Tesla to ensure the 450 megawatt-hour energy storage project is ready for the Australian summer, which begins in December. Testing will resume on Wednesday. “We have taken the time to understand the cause of the incident and we have implemented actions to ensure it will …