A former lab technician at DuPont’s La Porte, Texas, herbicide plant has filed a lawsuit against the Delaware chemical giant, claiming she was terminated because of her repeated reporting of safety violations shortly before a leak of 24,000 lbs of methyl mercaptan killed four employees at the facility.

Barbara Acker, who is seeking $1 million as compensation for lost wages, emotional distress and violation of Texas employment law, told the newspaper Houston Chronicle she made both written and verbal complaints to DuPont for five years regarding violations in how the company stored and handled chemicals.

Following a series of accidents at plants in Texas, New Jersey and Louisiana, DuPont is already under scrutiny. In July, the US Occupational Safety and Health Administration (OSHA) placed the company on the five-year-old Severe Violator Enforcement Program list of problem companies, citing its failure to correct safety violations such as rundown equipment, undertrained workers and undisclosed hazards.

In its preliminary investigation into the La Porte leak, the US Chemical Safety Board (CSB) also was critical of DuPont’s safety procedures.

Earlier, in May, OSHA proposed fines totaling $99,000 for violations related to the Texas fatalities, saying the chemical producer had “demonstrated indifference towards creating a safe and healthy workplace by committing willful or repeated violations, and/or failing to abate known hazards.”

DuPont is contesting all the OSHA fines. However, two unions representing hourly workers at the company and its recent spinoff Chemours, which now owns one of the cited plants, have called on management to cooperate with workers in resolving safety issues rather than fighting the charges.