Federal investigators release report on deadly Waukegan plant explosion

The explosion was felt 20 miles away, leveling the AB Specialty Silicones plant in Waukegan last May, killing four employees.

"The incident didn't need to happen, preventable,” said Dr. Kristen Kulinowski, U.S. Chemical Safety Board. 

Federal investigators Wednesday released a 21-page fact-finding report on the fatal accident, which started when employees poured chemicals into a giant mixing tank.

"The tank made a very strange sound and erupted,” said Tamara Qureshi, U.S. Chemical Safety Board. “Witnesses describe a hot and smoky scene as material overflowed from the tank and spilled onto the floor."

Hydrogen gas, which is extremely flammable, began to circulate through the building, but it's unclear whether employees were aware of the imminent danger.

“The CSB determined that there were no flammable gas detectors or hydrogen gas detectors with alarms to warn workers of the significant hazard,” said Qureshi.

A shift supervisor ordered workers to turn on exhaust fans, but before they could act, the building exploded.

Investigators say the goal of the report is to find areas where safety standards can be improved.

"It's not our role to assign blame but to produce a factual report with some analysis that draws conclusions and recommendations for prevention,” said Dr. Kulinowski. 

They're also focusing on the placement of the ventilation system, which was right next to the mixing tank and may have inadvertently circulated the hydrogen gas throughout the building.

“The design of the building is still very much an area of active investigation for us,” said Dr. Kulinowski. 

Federal investigators say they're waiting for AB Specialty to produce some key documents they need to do their final report, which may not come for another year.