WAMEGO ? Classes in Wamego public schools were canceled and a section of U.S. Highway 24 was closed after a fire at the Wamego Concept Foods Inc. plant sent dense smoke billowing into the air.

Wamego Fire Chief Phil Stultz said no serious injuries were reported in Thursday’s blaze at Concept Foods, which sits along U.S. 24. One employee was temporarily trapped inside the building, but firefighters were able to get him out unharmed.

Stultz said the fire was probably the most significant and costly in Wamego history.

Concept Foods owner Bernie Hansen said the plant was open 24 hours a day.

About two dozen employees escaped from the building unharmed.

Wamego Supt. Doug Conwell closed all of the northeast Kansas district’s schools in case the smoke was toxic.

“I didn’t want to put any students in danger,” Conwell said.

High school seniors will take their remaining finals today and attend a practice graduation in the old gym.

Two apartment buildings and some businesses near the plant, including a Dollar General Store and a Pizza Hut, also were closed Thursday. A section of U.S. 24 was shut down for most of Thursday morning as more than 50 firefighters fought the blaze.

Concept Foods processes, cooks and packages meat entrees at plants in Alma and Wamego. The entrees are marketed by Austin, Minn.-based Hormel Foods.

Hansen shifted the Wamego factory’s workload to the Alma plant and Hormel Foods plants in Nebraska. Hansen said he expected losses to be in the millions, but that he would keep a plant in Wamego.

The cause of the fire remains under investigation.