A truck fire about 8 miles south of Prosser blocked Highway 221 for about four hours.
Benton County Fire District 5 arrived at the burning truck around 11:02 a.m. Saturday along the 26-mile highway connecting Prosser to Paterson.
They quickly put out the blaze and stopped it from spreading to a nearby wheat field, fire officials said.
No one was reported injured.
One lane of the highway was reopened around 12:30 p.m. The rest of the road was cleared at 3 p.m., the Washington State Department of Transportation said.