ISTANBUL

Three individuals remain unaccounted for after a large explosion occurred at a plant in the US state of Nebraska on Tuesday, the officials said.

The explosion occurred around midday at Horizon Biofuels, a manufacturer of fuel pellets and animal bedding based in Fremont, about 40 miles northwest of Omaha, according to ABC News.

“When we arrived on scene, we had heavy smoke and a lot of flames coming out,” Fremont Fire Chief Todd Bernt said during a news briefing Tuesday afternoon. “We had a lot of structural collapse.”

Fremont Mayor Joey Spellerberg said three people were inside the plant at the time of the explosion. “But that’s all we can say at this point,” he added.

Bernt said firefighters have been unable to enter the building to search for the missing individuals due to the structural damage.

The fire department has called in Nebraska Task Force One, which is assessing how to safely conduct a search, Bernt said.

The cause of the explosion is under investigation as the Nebraska State Fire Marshal’s Office and other agencies responded to the scene.

Nebraska Gov. Jim Pillen said he is closely monitoring the situation.

“Our thoughts and prayers are with all involved — and we’re ready to help any way we can,” Pillen said in a statement.