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Relatives of victims people killed in the March 2014 Oso mudslide reached a $50 million settlement Sunday with the State of Washington just one day before their lawsuit is scheduled to go to trial, lawyers for the families said.

The settlement, which must be approved by the judge overseeing the case, would dismiss almost all claims only hours before the civil trial was to have begun Monday in King County Superior Court.

"We believe it is in the interests of the plaintiffs and the State to bring this matter to a full conclusion," the lawyers said, more then 2½ years after 43 people were killed when the mudslide covered a square mile of Washington's Stillaguamish River Valley, destroyed 49 buildings and closed a state highway for six months.

Related: Oso Mudslide: Lawsuit Blames State, Logging Company for Deadly Disaster

One defendant in the case, a timber company accused of contributing to the danger of the slide zone, wasn't included in the settlement, meaning the civil trial was still scheduled to proceed Sunday night. The families are seeking unspecified damages.

The settlement is also separate from whatever punitive sanctions the judge might choose to assess against state lawyers for allegedly having deleted emails from experts hired to testify in the trial.