(Reuters) – A Sempra Energy subsidiary did not conduct detailed inspections or analyses of leaks at the Aliso Canyon natural gas storage facility in California before the major 2015 leak that has cost the utility more than $1 billion and generated hundreds of lawsuits, according to a state report released on Friday. The long-awaited report, an independent analysis of the cause of the 2015 leak commissioned by the state’s public utility and oil and gas regulatory agencies, found the leak occurred because contact with groundwater caused microbial corrosion that led to the rupture of a well casing. SoCalGas, as the utility is known, never conducted failure investigations on 60 casing leaks at the Los Angeles area gas storage facility going back to the 1970s, the report by Blade Energy Partners found. In a statement, SoCalGas said the California Public Utilities Commission’s (CPUC) report confirmed that it was in compliance with natural gas storage regulations in place at the time of the leak. The ruptured well spewed more than 4 billion cubic feet of natural gas into the air over nearly four months from October 2015 to February 2016, prompting outcries from the suburban communities near the facility that became a public relations nightmare for the utility. More than 8,000 households and two schools were relocated during the leak. SoCalGas has said it still faces 394 lawsuits, including 48,500 plaintiffs. The CPUC and the state’s Division of Oil, Gas, and Geothermal Resources said updated well safety regulations put in place since the leak largely address the report’s recommendations.