RALEIGH, N.C. (AP) — Dozens of insurance companies say they're not obligated to help pay for Duke Energy Corp.'s multi-billion dollar coal ash cleanup because the nation's largest electric company long knew about but did nothing to reduce the threat of potentially toxic pollutants.

The claim is in a filing by lawyers for nearly 30 international and domestic insurance companies that were sued by Duke Energy in March to force them to cover part of the utility's coal ash cleanup costs in the Carolinas.

The 57 policies generally promise to help Duke pay what it's legally obligated to pay for prope...