At least three people, including two young girls, died after a powerful explosion at Horizon Biofuels in Fremont, Nebraska, on Tuesday. The blast, caught on security cameras, caused the building to collapse and sent black smoke into the sky. Fires are still burning, and the structure remains too dangerous to enter.

Fremont Mayor Joey Spellerberg said the explosion happened just before noon. A male employee and his two daughters, who were waiting for him before a doctor’s appointment, were believed to be near the grain bin at the time. “My heart hurts,” said Spellerberg. “We pray for all the families involved.”

Emergency responders, including the Nebraska State Patrol and nine volunteer fire departments, have been working to control the fire and assess the scene. Fire Chief Todd Bernt explained, “Due to the collapse, with the mangled steel, we were unable to get inside.”

Drones are being used to monitor the area, and a three-mile radius remains blocked off. The plant, which also caught fire in 2014, stored wood and fuel pellets.

Nebraska Governor Jim Pillen said his office is supporting the city and added, “Our thoughts and prayers are with all involved.”