Story highlights Boiler explodes at St. Louis factory

Debris shoots through roof and kills two in another building

(CNN) 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 a.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.

Parts of a boiler damaged several buildings in St. Louis.

"We have not measured it (boiler debris) yet but estimate it to be about a ton and a half. It's huge," Mosby said.

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