On Monday, an explosion sent a massive boiler crashing through the roof of a St. Louis box company and smashed much of it down hundreds of feet away into a neighboring laundry business. Three people were killed and four others injured.

Deadly explosion:

At about 8am, one person died in the explosion at the Loy-Lange Box Co, while two more died when a large piece of the van-sized boiler crashed into the Faultless Healthcare Linen building, according to Fire Chief Dennis Jenkerson.

Jenkerson said that investigators were trying to pinpoint what caused the boiler to blow up at the building in a largely industrial area of south St.Louis.

The boiler, which was said was roughly 4 feet in diameter and 10 feet long, and weighed about a ton-and-a-half, pinned down a linen company worker who is now in critical condition, along with another person of the four survivors.

Jenkerson said the boiler had traveled up to 500 feet and that it was still hot when rescuers arrived.

As of early Monday afternoon, none of the victims’ names have been released.

Jenkerson added that a piece of pipe, about 8 feet long, linked to the blast smashed through the roof of a third building, badly damaging it.

Investigators will seek out and review the boiler’s inspection and maintenance records, despite believing initially that the explosion was accidental.

It’s not yet clear whether anyone was working on the boiler at the time of the deadly incident.

On the company’s website, Loy-Lange Box Co is described as a ‘full-service corrugator and custom box manufacturer.’

A spotty record:

Also working on the scene were investigators from the US Department of Labor’s Occupational Safety and Health Administration. Scott Allen, OSHA spokesman, said the agency’s records show that Loy-Lange has paid fines for workplace violations three times since 2014.

In August 2016, the company paid a $3,741 fine after inspection found holes in floors that prevented proper cleaning. While in November 2014, another inspection found defective equipment, including a forklift without lights and damage to some safety latches.

The company was fined $6,566, and in February 2014, the company paid $2,450 for defective energy control procedures, such as not properly training employees to ensure machinery was turned off and powered down.