LAMAR, Neb. -- A fire at a fertilizer plant in southwest Nebraska has been extinguished.

Chase County fire officials say the blaze at the site formerly known as Lamar Fertilizer, was out as of mid-afternoon Thursday. 

The fire was located about six miles outside of Lamar, or 23 miles west of Imperial. 

At its worst, smoke from the fire forced authorities to close down U.S. Highway 6 from Imperial to the Colorado border. Authorities said the fire could also involve chemicals.

The Chase County Sheriff's Office told people to stay away from the area, and advised people stay out of the smoke plume and shelter in place. 

Traffic was rerouted onto county roads muddied by falling snow. Witnesses say semi-tractor-trailers and on-lookers were sliding off roads into ditches because of the muddy conditions.

There's been no word on what caused the fire. No one was injured.