The fire broke out at about 4 a.m. Thursday when a refueling truck burst into flames at the plant along Highway 97-A about six miles north of Wenatchee near the Rocky Reach Dam, the Washington State Patrol reported.
From there, the fire may have spread to other chemicals at the plant. Smoke was reported to be billowing from the site, and the highway was closed.
Fire crews rushed to the scene. Authorities at first were planning to evacuate about 30 homes in the area as a precaution, but later it was determined that this step was not necessary.
Smoke was continuing to billow from the scene after sunrise as fire crews kept up their attack on the blaze.
A state Department of Transportation spokesperson said Highway 97-A should reopen in the area by 7 or 7:30 a.m.
Check back later for further updates to this story.