OAKWOOD VILLAGE, Ohio (WJW) — Local, state and federal investigators are now trying to determine what caused a massive fatal explosion and fire at I. Schumann & Company foundry.

On Tuesday, Oakwood Village Fire Department Capt. Brian DiRocco confirmed the State Fire Marshal is leading the investigation along with OSHA, EPA and ATF agents, but he said progress is slow due to the devastation.

“The interior of the building is pretty catastrophic,” said DiRocco. “Right now, we’re working with a structural engineer to see where it’s safe to conduct our investigation, the damage is pretty extensive.”

Also Tuesday, dozens of 911 calls were released as workers, witnesses and residents desperately called for help.

One panicked woman said, “Something just blew up down the street. There’s a huge thing of smoke, my house just shook, oh my God.”

The explosion happened just before 2:30 p.m. Monday according to officials.

Sixty firefighters and first responders from 14 departments provided mutual aid and it still took more than two hours to contain the ferocious blaze.

“You thought a bomb went off,” said witness Greg Strichek.

“There were several people that suffered burn injuries,” said Capt. DiRocco, “ I don’t know if it was from the molten product or the fire or the heat.”

Thirteen people were transported to area hospitals. Other workers could be heard calling 911 for help after they had returned home. And sadly a 46-year-old employee passed away at the scene.

In a statement I. Schumann & Company said in part: “It is with heavy hearts that we confirm the passing of Steven Mullins, one of our valued colleagues and good friend to all. Steve was with the company for nearly 30 years working in our maintenance group. He will be greatly missed, and our thoughts are with his family at this time.”

The company went on to thank the “many first responders” for their quick actions and said they are cooperating with OSHA and “working with our employees regarding their needs while the facility is idle.”

It’s unknown how long the investigation might take. The debris field is vast. When the building exploded, large chunks of concrete and metal went sailing through the air and landed up to 200 yards away from the structure on Alexander Road.

Nearby businesses spent the day cleaning up. Directly across the street, employees with Northern Haserot said they’re building sustained thousands of dollars in damages.

“Fragments of molten steel, we had an I-beam go through the roof behind me,” said Strichek.

Everyone seemed still stunned.

The 4th generation company’s been in business since 1917 and, according to fire inspectors, in good standing.

Former employees told Fox 8 News that’s why they had to see the damage in person. They just can’t fathom how the foundry exploded.

“That’s why we came out to see it. It’s like, holy cow,” said former employee Douglas Chismar.