A boiler exploded at a factory in St. Louis, spewing debris and leading to three deaths in multiple buildings, fire officials said.
The explosion initially killed one person, injured another and left several people trapped about 7:30 p.m. at the Loy-Lange Box Company near downtown St. Louis.
The blast sent a piece of debris about the size of a large cargo van through the factory roof. It traveled about 500 feet and killed two people when it landed, officials said.
The two were employees on their first day of work at Faultless Healthcare Linen Company, a medical laundry company, said Capt. Garon Mosby with the St. Louis Fire Department.
"We have not measured it (boiler debris) yet but estimate it to be about a ton and a half. It's huge," Mosby said.
Another person was injured at the laundry company and taken to a hospital in critical condition, fire officials said.
A third building was damaged when a pipe penetrated its roof, but no injuries were reported, fire officials said.
The Loy-Lange boiler was used to provide steam for the entire factory and it was unclear whether it recently underwent maintenance, St. Louis Fire Chief Dennis Jenkerson told CNN affiliate KMOV.
It's also unclear what caused the explosion and whether someone was working on the boiler at the time of the incident, but foul play is not suspected, Jenkerson said.
"We are going to be looking at all the records and make sure that everything was up to date," he said.