What is the burden of proving that there is no evidence of a hostile fire in a claim for damages under a policy that excludes from the general exclusion of damage caused by pollution?

We were previously presented with this question and noted that the "California courts have not decided which party has the burden of proving an exception to an exclusion." Maffei v. Northern Ins. Co., 12 F.3d 892, 899 (9th Cir.1993). In that case, however, we were not required to resolve the issue. The policy at issue there excepted damages caused by a hostile fire from its general exclusion of damage caused by pollution. Id. at 895. We rejected plaintiff's assertion that the district court had impermissibly shifted the burdens of proof. Id. at 900. Rather, we found that the district court, in granting summary judgment, simply found "as a threshold matter, [that] there was no evidence that a fire had occurred." Id. Because the district court had erroneously excluded a declaration offered by the insured, we concluded the district court erred in finding that no question of fact existed as to whether a fire had occurred. Id. We held that, as the moving party, the insurer had failed to meet its burden of showing the absence of a question of fact. Id. In other words, a material issue existed about application of the exception. Id.