FREMONT, Neb. (AP) — Officials confirmed Wednesday that two girls and an adult, who had been missing since a massive explosion tore through a Nebraska biofuels plant, are dead. Firefighters have been battling the smoke and flames, which have been smoldering in the wreckage for nearly a day.

“Right now this has moved to a recovery effort,” Fremont Mayor Joey Spellerberg said at a news conference.

Spellerberg explained that the children were at the plant waiting for an employee to finish work so they could attend a doctor’s appointment together. Although he was unsure of their exact ages, he stated both girls were under 12 years old.

After Tuesday’s explosion, photos revealed the devastation: the plant’s tall tower was destroyed, leaving twisted metal and exposed siding. Debris was scattered across the ground, and nearby residents reported feeling their homes tremble from the blast.

The fire has prevented crews from getting close enough to the Horizon Biofuels plant to search for the missing people inside, ther mayor said.

“We had a fire going all night, even through the rain,” Spellerberg told radio station KFAB in Omaha earlier Wednesday.

“You have the feed mill area, you have the office area just under flames, basically it has not stopped,” Spellerberg said.

Fremont Fire Chief Todd Bernt shared that the first responders faced “heavy smoke and a lot of flames” upon arriving at the site, which is in proximity to other manufacturing and food processing facilities.

The plant, which produces animal bedding and wood pellets for heating and smoking food, utilizes large amounts of wood waste. Bernt mentioned that the facility is believed to store wood and alcohol-based materials. In 2014, a fire had damaged the building’s electrical system, but the structure had remained intact, as reported by the Fremont Tribune.

Taylor Kirklin, living about half a mile (0.8 kilometers) from the site, recounted how her entire house shook during the explosion on Tuesday. The noise was so intense that she initially thought a car had crashed into the dog kennel business her family operates on their property.

“I got up and looked outside and there was a huge plume of smoke,” she said. “We were really unsure when the explosion happened which plant it was, because there are so many in that area.”

Fremont, a city of about 27,000 and the sixth-largest in Nebraska, is 32 miles (52 kilometers) northwest of Omaha.