FREMONT, Neb. (AP) Two girls and an adult missing since a huge explosion tore through a Nebraska biofuels plant are confirmed dead, officials said Wednesday, as firefighters have battled smoke and flames smoldering in the wreckage for nearly a day.

“My heart hurts,” Fremont Mayor Joey Spellerberg said at a news conference. “It’s a tragedy. We pray for every person involved.”

Spellerberg said the two children were waiting for the employee to get off work so they could go to a doctor’s appointment. He wasn’t sure of their exact ages but said both were under age 12.

Photos taken after Tuesday’s blast show the plant’s tall tower torn off, exposing mangled metal and ripped siding. Debris littered the ground, and nearby residents say the blast shook their homes.

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

Fremont Fire Chief Todd Bernt said first responders were up against “heavy smoke and a lot of flames” when they first arrived at the facility, which is surrounded by other manufacturing and food processing plants.

The plant makes animal bedding and wood pellets for heating and smoking food, using tons of wood waste, and Bernt said they believe the facility stores wood and some alcohol-based materials. A 2014 fire at the building had damaged the electrical system but left the structure intact, according to reporting by the Fremont Tribune.

Taylor Kirklin, who lives about a half mile (0.8 kilometers) from the building, said her whole house shook Tuesday. She said the explosion was so loud that she thought someone had crashed a car into her family’s dog kennel business on the 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.