The U.S. Chemical Safety Board has released its report on a fatal blast at a Tonawanda plant.
The investigation found 'sparks or heat' from welding on top of a storage tank likely ignited flammable vapors inside the tank - a hazard which had been overlooked by DuPont engineers.
The November 2010 blast at the River Road facility killed one contractor - and it came less than a year after three similar incidents - including one fatality - at another DuPont plant.
In Buffalo Thursday, CSB Chairperson Rafael Moure-Eraso said the main message is repairing tanks or "hot work" is a common yet dangerous activity.
"Hot work incidences across the country continue to cause death, injury property damages with with alarming frequency," said Moure-Eraso.
In a written statement, DuPont Plant Manager Ronald Lee said "safety is a core value at DuPont" and "many improvements" have been made at the Tonawanda plant since the incident.
In May - OSHA cited DuPont with numerous violations and proposed more than 60-thousand-dollars in fines.