After its explosive early history of concussing gunpowder plants and lead-poisoned factories, DuPont Co. claims credit for pioneering modern chemical safety. The Wilmington-based company has even built a safety-consulting business based on teaching other companies how to improve processes the DuPont way.

But on Thursday, just as DuPont had finished spinning off a constellation of aging chemical plants into a separate firm - Chemours Co. - government investigators said they were putting DuPont on the five-year-old Severe Violator Enforcement Program list of problem companies, next to hundreds of much smaller firms, including the wreckers blamed for the fatal Salvation Army thrift store collapse in Philadelphia.

The U.S. Occupational Safety and Health Administration gave DuPont that unwanted status after reviewing 2014 accidents at DuPont plants in Texas, New Jersey, and Louisiana. It cited failures to correct safety violations such as rundown bits of equipment, undertrained workers, and undisclosed hazards. Four workers died in the Texas accident.

OSHA says DuPont earned its "Severe Violator" tag because it "demonstrated indifference towards creating a safe and healthy workplace by committing willful or repeated violations, and/or failing to abate known hazards."

"DuPont promotes itself as having a 'world-class safety' culture and even markets its safety expertise to other employers, but these four preventable workplace deaths and the very serious hazards we uncovered at this facility are evidence of a failed safety program," Dr. David Michaels, OSHA assistant director, said in the statement.

"We here at OSHA want DuPont and the chemical industry as a whole to hear this message loud and clear," he said.

DuPont defended its response to the tragedy and OSHA's most recent complaints about the herbicide and hydrofluoric acid units at the Texas plant.

"We believe we have identified and are addressing most if not all of OSHA's significant findings," DuPont said. "We have shut down the herbicide unit in order to take corrective measures, and the unit will not restart until the work is complete." The hydrofluoric unit is now safe to operate, DuPont added.

DuPont also summoned history in its defense: Citing safety rules it says it began writing at its Brandywine gunpowder mills in 1811, the company said it has waged "a continuous process to improve ever since."

Therefore, "DuPont is disappointed with OSHA's classification, and we will be working with the agency to understand its decision," the company said. OSHA allows "informal" discussions and formal appeals; DuPont hasn't said which it will try. "We have not had a chance to review OSHA's findings in detail; we will work with the agency to better understand the citations and any further required abatement." DuPont concluded: "Safety is our number one priority."

Beyond the Texas deaths, OSHA added, DuPont "was cited at their Darrow, Louisiana facility in November 2014 and Deepwater, New Jersey facility in December 2014 for similar process safety management violations."

At DuPont's Chambers Works in Deepwater, which has since been spun off to Chemours, OSHA cited DuPont for eight "serious" and two "repeat" violations: for failing to map pipe, valve, and instrument arrangements fully or correctly; failing to make clear that toxic chemical monitors in one location had been removed; wrongly identifying plant operators as "hazardous materials technicians"; failing to fix a rundown pump that threatened to spill ammonia solution on workers; taking "an unreasonable amount of time" to document an electrical system operating near flammable hydrogen gas; and repeated failure to improve storage, transportation, and test equipment used with highly useful but also corrosive and toxic hydrofluoric acid as it is moved and stored in half-ton containers.

DuPont continues to offer other companies operating advice learned over its long and complex history. "DuPont Sustainable Solutions' safety consulting business has worked with more than a thousand clients in 100 countries around the world to train their employees in best in class safety practices," spokeswoman Kate Bailey told me in an e-mail.

"Many of our clients have achieved significant reductions in their safety incident and injury rates as a result of our safety consulting services, and this is backed up by solid supporting data."

But OSHA's findings at the LaPorte, Texas, pesticide plant where the workers died last year make the company look hypocritical, say leaders of the International Chemical Workers Union Council, an affiliate of the United Food and Commercial Workers, which represents workers at LaPorte.

"It is time to reevaluate, if not reject, your training safety model," Frank Ciphers, the union's president, wrote in an open letter after OSHA levied a previous round of fines at the site last month.

Correction: An earlier version of this article misidentified the Philadelphia building that collapsed, killing six, in 2013.