Fire destroyed a maintenance building and the semi-trailer trucks within and around it Monday at the Red Stag Trucking Co.
Portales Fire Chief T.J. Cathey said it started when sparks from maintenance operations contacted flammable materials inside the building.
Cathey said the flammable material could not be isolated.
"There were a number of flammable materials in use" in the building at the time, Cathey said.
Cathey said there were "quite a few" people inside the building when the fire broke out, but all escaped safely and gathered at the gas pumps of the nearby Walmart store in Portales.
The fire, which started just before 2 p.m. Monday, was not declared contained until 8:20 Tuesday morning, Cathey said.
The blaze sent up a column of black smoke that was visible for miles.
Witnesses reported many explosions from the fire; Cathey said those explosions were from semi-truck tires blowing out from the heat of the blaze.
Firefighters from Portales, Arch, and the Clovis Fire Department responded.
Red Stag hauls milk directly from dairies to major dairy plants including Borden, Oak Farms, Schepps, Daisy Brand and Blue Bell, according to the company website.
The company has been in Portales since 2015 and operates about 200 trucks from "coast to coast," the website reports. It wasn't immediately clear how many trucks were damaged or destroyed in Monday's blaze.
U.S. 70 was closed for "about 30 minutes" after firefighters arrived at the scene, Cathey said, but traffic was resumed later, with only one northbound lane closed. The road was opened completely some time Monday night, Cathey said.