An “avian incident” sparked a fire at one of California’s biggest solar farms, affecting 1,200 acres and knocking out 84% of the California Valley Solar Ranch’s generating capacity.

The June 5 incident didn’t damage solar panels at the 250-megawatt power plant, but distribution poles and cables need to be replaced, according a regulatory filing Wednesday from owner Clearway Energy Inc. The company didn’t say exactly how the blaze was ignited.