Three people inside a Nebraska manufacturing building that partially collapsed in an explosion Tuesday evening remained missing as authorities tried to reach them.

Rescuers have been thwarted by the state of the mangled, warehouse-style building that appears to have been made of steel and corrugated metal walls, Fremont Fire Chief Todd Bernt said at a late-afternoon news conference.

A federally organized search-and-rescue task force based in Lincoln will tunnel through the debris if necessary to get to the three people, Bernt said.

“We are unable to gain access early on,” the chief said. “We tried to get access, but just due to the collapse with the mangled steel, we’re unable to get inside.”

Asked about the status of the three, the chief said they were unaccounted for. It wasn’t clear if they were employees.

The blast was reported a few minutes before noon at the location, where wood pellets for fuel are made by Horizon Biofuels, Inc., authorities said. The company also makes pet bedding under the name Elkhorn Valley Animal Bedding, according to NBC affiliate WOWT of Omaha.

A contact for Horizon Biofuels did not immediately respond to a request for comment.

Smoke rose over the community at the southern end of the city, and the fire was still smoldering and could continue to do so for days, Bernt said.

City officials said drinking water was unaffected and air quality was not dangerous, though residents downwind should avoid breathing in smoky air. Nebraska Department of Water, Energy, and Environment representatives did not immediately respond to a request for comment.

Nebraska State Patrol responded to the explosion and asked people to avoid the area, according to a statement. The cause of the blast was under investigation.

“We will continue to closely monitor the explosion in Fremont in coordination with local responders, law enforcement, and state partners,” Gov. Jim Pillen said on X. “Our thoughts and prayers are with all involved — and we’re ready to help any way we can.”