The U.S. government is threatening to sue PacifiCorp, a unit of Warren Buffett’s Berkshire Hathaway, to recover nearly $1 billion in costs related to the 2020 wildfires in southern Oregon and northern California, though the company is trying to negotiate a settlement.

The potential lawsuits were disclosed in an annual report filed by PacifiCorp’s Iowa-based parent company, Berkshire Hathaway Energy, on Monday — two days after Buffett lamented the disappointing results at the conglomerate’s utility division in his annual letter to Berkshire Hathaway shareholders. This new liability comes after the utility already agreed to pay hundreds of millions of dollars in lawsuits related to the fires.

In its annual report, Berkshire Hathaway Energy said the U.S. Justice Department told the company it is seeking $625 million in firefighting and cleanup costs related to the September 2020 Archie Creek and Susan Creek fires. Oregon’s Justice Department said it is also seeking $109 million in damages related to those fires.

In addition to that, the U.S. Forest Service has asked PacfiCorp to pay $356 million for firefighting costs and damages related to the Slater Fire that started in California but also crossed over the border into Oregon.

The fires were among the worst natural disasters in Oregon’s history. They killed nine people, burned more than 1,875 square miles (4,856 square kilometers) and destroyed upward of 5,000 homes and other structures.

The Oregon lawsuits say PacifiCorp negligently failed to shut off power to its 600,000 customers during a windstorm over Labor Day weekend in 2020, despite warnings from state leaders and top fire officials, and that its power lines caused multiple blazes.

Representatives of PacifiCorp and Berkshire Hathaway Energy declined to comment about the new liabilities. The Justice Department didn’t immediately respond to a request for comment about the potential lawsuits.

Omaha, Nebraska-based Berkshire estimates that its utilities face at least $8 billion in claims across all the wildfire lawsuits already filed in Oregon and California although the damages could be doubled or even tripled in some of those cases and some of the lawsuits don’t list a dollar amount.

Those costs, combined with the uncertain regulatory environment in western states where wildfires have become more prevalent, are making it harder for utilities like PacifiCorp to decide when it makes sense to invest in major new power plants and transmission lines.

“It will be many years until we know the final tally from BHE’s (Berkshire Hathaway Energy’s) forest-fire losses and can intelligently make decisions about the desirability of future investments in vulnerable western states,” Buffett said in his letter. “It remains to be seen whether the regulatory environment will change elsewhere.”

Buffett said that in extreme cases like with Pacific Gas and Electric in California or Hawaiian Electric utilities could face bankruptcy and the country may have to decide whether to turn to public power if private investors are no longer willing to take the risks associated with the utility business.