The US Environmental Protection Agency brought sensors into the area, but so far, the detectors have found nothing that requires additional evacuations or precautions beyond those already taken, according to EPA officials on the scene.
The blaze prompted officials to evacuate homes and schools near the plant, which sits at the intersection of two major highways, and people farther afield were encouraged to stay indoors and close windows.
The fire, which sent a plume of black smoke billowing into the air much of the day, is about 90 percent contained, according to local fire officials.
Officials say no one at the plant or in the surrounding area has been injured.
Fire officials say the blaze broke out around 11 a.m. as workers at Magnablend, Inc.'s facility were mixing chemicals. The company blends and packs liquid and powdered chemicals for a range of activities from farming and oil production to cleaning products for industry.
Among the liquids at the facility: large quantities of ammonia and several forms of acid, including sulfuric and hydrochloric acid.